Magnetic Tunnel Junction Cell Including Multiple Vertical Magnetic Domains

ABSTRACT

Magnetic tunnel junction cell including multiple vertical domains. In an embodiment, a magnetic tunnel junction (MTJ) structure is disclosed. The MTJ structure includes an MTJ cell. The MTJ cell includes multiple vertical side walls. Each of the multiple vertical side walls defines a unique vertical magnetic domain. Each of the unique vertical magnetic domains is adapted to store a digital value.

I. FIELD

The present disclosure is generally related to a magnetic tunneljunction cell including multiple vertical magnetic domains.

II. DESCRIPTION OF THE RELATED ART

In general, widespread adoption of portable computing devices andwireless communication devices has increased demand for high-density andlow-power non-volatile memory. As process technologies have improved, ithas become possible to fabricate magneto-resistive random access memory(MRAM) based on magnetic tunnel junction (MTJ) devices. Traditional spintorque tunnel (STT) junction devices are typically formed as flat stackstructures. Such devices typically have two-dimensional magnetic tunneljunction (MTJ) cells with a single magnetic domain. An MTJ celltypically includes a fixed magnetic layer, a barrier layer (i.e., atunneling oxide barrier layer, MgO, Al₂O₃, etc,), and a free magneticlayer, where a bit value is represented by a magnetic field induced inthe free magnetic layer and an anti-ferromagnetic film (AF) layer.Generally, MTJ devices may also include additional layers. A directionof the magnetic field of the free layer relative to a direction of afixed magnetic field carried by the fixed magnetic layer determines thebit value.

Conventionally, to improve data density using MTJ devices, one techniqueincludes reducing the size of MTJ devices to put more MTJ devices in asmaller area. However, the size of the MTJ devices is limited by thecritical dimension (CD) of fabrication technology. Another techniqueinvolves forming multiple MTJ structures in a single MTJ device. Forexample, in one instance, a first MTJ structure is formed that includesa first fixed layer, a first tunnel barrier, and a first free layer. Adielectric material layer is formed on the first MTJ structure, and asecond MTJ structure is formed on top of the dielectric material layer.Such structures increase the density of storage in an X-Y directionwhile increasing a size of the memory array in a Z-direction.Unfortunately, such structures store only one bit per cell, so the datadensity in the X-Y direction is increased at the expense of area in aZ-direction and may double a MJT manufacturing cost. Further, suchstructures increase wire-trace routing complexity. Hence, there is aneed for improved memory devices with greater storage density withoutincreasing a circuit area of each of the MTJ cells and that can scalewith the process technology.

III. SUMMARY

In an embodiment, a magnetic tunnel junction (MTJ) structure isdisclosed. The MTJ structure includes an MTJ cell. The MTJ cell includesmultiple vertical side walls. Each of the multiple vertical side wallsdefines a unique vertical magnetic domain. Each of the unique verticalmagnetic domains is adapted to store a digital value.

In another embodiment, a device is disclosed that includes a singlemagnetic tunnel junction (MTJ) cell adapted to store multiple digitalvalues. At least one of the multiple digital values is stored using avertical magnetic field. The device also includes multiple terminalscoupled to the MTJ cell.

In another embodiment, a method of fabricating a device is disclosed.The method includes performing a deep trench photo and etch process tocreate a deep trench in a substrate, such as an oxide interlayerdieletric substrate. The method includes depositing a bottom electrodeinto the deep trench. The method includes depositing layers to form amagnetic tunnel junction (MTJ) structure including a fixed layer, atunnel barrier, and a free layer. Additional layers may be included,such as an anti-ferromagnetic film (AF) layer. At least a first portionof the MTJ structure is coupled to the bottom electrode. The method alsoincludes depositing a top electrode onto at least a second portion ofthe MTJ structure. The method further includes performing magneticanneal process on the MTJ structure in a horizontal direction and in avertical direction. The horizontal direction is substantially parallelto a plane of the substrate and the vertical direction is substantiallynormal to the plane of the substrate. A first portion of the free layerhas a first magnetic domain in the vertical direction, and a secondportion of the free layer has a second magnetic domain in the horizontaldirection.

One particular advantage provided by embodiments of the magnetic tunneljunction (MTJ) device including multiple vertical magnetic domains isprovided in that multiple digital values may be stored at a single MTJcell. For example, a single MTJ cell may be configured to store up tofour or more bits. A MTJ having four bits can store up to sixteen logicstates in each MTJ cell.

Another particular advantage is provided in that the multiple-bit MTJcell can scale with process technology, allowing for multiple bits perMTJ cell even as the MTJ cell size decreases.

Still another particular advantage is provided in that the MTJ cell caninclude multiple independent magnetic domains to store digital values.In a particular embodiment, the MTJ cell can include multiple sidewalls(extending vertically from a planar surface of a substrate), where eachof the multiple sidewalls carries a unique vertical magnetic domain tostore a data bit. Additionally, the MTJ cell can include a bottom wallincluding a horizontal magnetic domain to store another data bit. Forexample, the MTJ cell can include three sidewalls in variousorientations, two sidewalls in a face-to-face orientation or inconjunction, or a single sidewall, in various embodiments.

Yet another particular advantage is provided in that vertical magneticdomains enable increased MTJ cell density with reduced device footprint.

Yet another particular advantage is provided in that the MTJ cell caninclude multiple independent magnetic domains that may be written to orread from without changing data stored at other magnetic domains withinthe MTJ cell.

Other aspects, advantages, and features of the present disclosure willbecome apparent after review of the entire application, including thefollowing sections: Brief Description of the Drawings, DetailedDescription, and the Claims.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a particular illustrative embodiment ofa magnetic tunnel junction (MTJ) cell including multiple verticalmagnetic domains that can be used to store multiple digital bits;

FIG. 2 is a cross-sectional view of a magnetic tunnel junction cellincluding multiple vertical magnetic domains that is adapted to storemultiple digital bits;

FIG. 3 is a top view of a particular illustrative embodiment of a memorydevice including a magnetic tunnel junction (MTJ) cell with multiplevertical magnetic domains;

FIG. 4 is a cross-sectional view of the memory device of FIG. 3 takenalong line 4-4 in FIG. 3;

FIG. 5 is a cross-sectional view of a second particular illustrativeembodiment of a memory device including a magnetic tunnel junction (MTJ)cell with multiple vertical magnetic domains;

FIG. 6 is a cross-sectional view of a third particular illustrativeembodiment of a memory device including a magnetic tunnel junction (MTJ)cell with multiple vertical magnetic domains;

FIG. 7 is a top view of a particular illustrative embodiment of amagnetic tunnel junction (MTJ) stack with multiple vertical magneticdomains where the MTJ cell is written in a bit zero state;

FIG. 8 is a diagram of a particular illustrative embodiment of layers ofa magnetic tunnel junction (MTJ) stack illustrating a write zero currentflow direction;

FIG. 9 is a cross-sectional view of the MTJ stack of FIG. 7 taken alongline 9-9 in FIG. 7;

FIG. 10 is a cross-sectional view of the MTJ stack of FIG. 7 taken alongline 10-10 in FIG. 7;

FIG. 11 is a top view of a magnetic tunnel junction (MTJ) stack withmultiple vertical magnetic domains where the MTJ stack is written in abit one state;

FIG. 12 is a diagram of a particular illustrative embodiment of layersof a magnetic tunnel junction (MTJ) structure illustrating a write onecurrent flow direction;

FIG. 13 is a cross-sectional view of the MTJ stack of FIG. 11 takenalong line 13-13 in FIG. 11;

FIG. 14 is a cross-sectional view of the MTJ stack of FIG. 11 takenalong line 14-14 in FIG. 11;

FIG. 15 is a top view of a fourth illustrative embodiment of a memorydevice including a magnetic tunnel junction (MTJ) cell with multiplevertical magnetic domains;

FIG. 16 is a cross-sectional view of the memory device of FIG. 15 takenalong line 16-16 in FIG. 15;

FIG. 17 is a top view of a fifth illustrative embodiment of a memorydevice including a magnetic tunnel junction (MTJ) cell with multiplevertical magnetic domains;

FIG. 18 is a cross-sectional view of the memory device of FIG. 17 takenalong line 18-18 in FIG. 17;

FIG. 19 is a top view of a sixth illustrative embodiment of a memorydevice including a magnetic tunnel junction (MTJ) cell with multiplevertical magnetic domains;

FIG. 20 is a cross-sectional view of the memory device of FIG. 19 takenalong line 20-20 in FIG. 19;

FIG. 21 is a top view of a seventh illustrative embodiment of a memorydevice including a magnetic tunnel junction (MTJ) cell with multiplevertical magnetic domains;

FIG. 22 is a cross-sectional view of the memory device of FIG. 21 takenalong line 22-22 in FIG. 21;

FIG. 23 is a top view of a second illustrative embodiment of a magnetictunnel junction (MTJ) stack with multiple vertical magnetic domainswhere the MTJ cell is written in a bit zero state;

FIG. 24 is a diagram of a second illustrative embodiment of layers of amagnetic tunnel junction (MTJ) stack illustrating a write zero currentflow direction;

FIG. 25 is a cross-sectional view of the MTJ stack of FIG. 23 takenalong line 25-25 in FIG. 23;

FIG. 26 is a cross-sectional view of the MTJ stack of FIG. 23 takenalong line 26-26 in FIG. 23;

FIG. 27 is a top view of a second illustrative embodiment of a magnetictunnel junction (MTJ) stack with multiple vertical magnetic domainswhere the MTJ stack is written in a bit one state;

FIG. 28 is a diagram of a second illustrative embodiment of layers of amagnetic tunnel junction (MTJ) structure illustrating a write onecurrent flow direction;

FIG. 29 is a cross-sectional view of the MTJ stack of FIG. 27 takenalong line 29-29 in FIG. 27;

FIG. 30 is a cross-sectional view of the MTJ stack of FIG. 27 takenalong line 30-30 in FIG. 27;

FIG. 31 is a diagram showing a cross-sectional view of a particularillustrative embodiment of a magnetic tunnel junction (MTJ) cell coupledto a bi-directional switch to read data from and to write data to theMTJ cell;

FIG. 32 is a diagram showing a cross-sectional view of a secondillustrative embodiment of a MTJ cell coupled to a bidirectional switchto read data from and to write data to the MTJ cell;

FIG. 33 is a diagram showing a cross-sectional view of a magnetic tunneljunction (MTJ) cell with multiple vertical magnetic domains and coupledto two switches to read data from and to write data to the MTJ cell;

FIG. 34 is a diagram showing a cross-sectional view of a particularillustrative embodiment of a magnetic tunnel junction (MTJ) cell withmultiple vertical magnetic domains and coupled to three switches to readdata from and to write data to the MTJ cell;

FIG. 35 is a diagram showing a cross-sectional view of a secondillustrative embodiment of a magnetic tunnel junction (MTJ) cell withmultiple vertical magnetic domains and coupled to three switches to readdata from and to write data to the MTJ cell;

FIG. 36 is a diagram showing a cross-sectional view of a magnetic tunneljunction (MTJ) cell with multiple vertical magnetic domains and coupledto four switches to read data from and to write data to the MTJ cell;

FIG. 37 is a flow diagram of a particular illustrative embodiment of amethod of fabricating a magnetic tunnel junction (MTJ) device withmultiple vertical magnetic domains;

FIG. 38 is a flow diagram of a second particular illustrative embodimentof a method of fabricating a magnetic tunnel junction (MTJ) device withmultiple vertical magnetic domains;

FIG. 39 is a flow diagram of a third particular illustrative embodimentof a method of fabricating a magnetic tunnel junction (MTJ) device withmultiple vertical magnetic domains;

FIG. 40 is a flow diagram of a particular illustrative embodiment of amethod of operating a magnetic tunnel junction (MTJ) device withmultiple vertical magnetic domains; and

FIG. 41 is a block diagram of a communications device including a memorydevice including magnetic tunnel junction (MTJ) cells.

V. DETAILED DESCRIPTION

FIG. 1 is a perspective view of a particular illustrative embodiment ofa magnetic tunnel junction (MTJ) cell 100 including multiple verticalmagnetic domains that can be used to store multiple digital values. TheMTJ cell 100 includes a magnetic tunnel junction (MTJ) stack having afixed magnetic layer 102, a tunnel junction layer 104, and a freemagnetic layer 106 arranged in a substantially rectangular shape. Anelectrode layer having a first sidewall portion 110, a second sidewallportion 112, a third sidewall portion 114 and a bottom wall portion 116is electrically and physically coupled to the fixed magnetic layer 102.A center electrode 108 is electrically and physically coupled to thefree layer 106. A first terminal structure 160 is coupled to the centerelectrode 108. A second terminal structure 162 is coupled to the firstsidewall 110. A third terminal structure 164 is coupled to the secondsidewall 112. A fourth terminal structure 166 is coupled to the thirdsidewall 114. A fifth terminal structure 168 is coupled to the bottomwall 116. The MTJ cell 100 may also include one or more additionallayers (not shown) between top and bottom electrode. For example, theMTJ cell 100 may include an anti-ferromagnetic (AFM) layer (not shown)to pin a magnetic field direction of the fixed layer 102. As anotherexample, the MTJ cell 100 may also include one or more synthetic fixedlayers or synthetic free layers (not shown) to enhance MTJ cellperformance, or additional anti-ferromagnetic (AFM) layers (not shown)to pin dual spin filter layer for dual spin filter MTJ operation. Inaddition, in a particular embodiment, an order of the layers 102-106 maybe reversed.

Each of the sidewalls 110, 112, and 114 are substantially rectangularand arranged so that the MTJ cell 100 has a U-shaped configuration whenviewed from above. In an alternative embodiment, the MTJ cell 100 mayinclude a fourth sidewall (not shown) coupled to a sixth terminalstructure (not shown) and may have a rectangular configuration whenviewed from above.

In a particular embodiment, a voltage may be applied to the centerelectrode 108 and an electrical current may flow from the centerelectrode 108 through the free layer 106, across the tunnel junction104, and through the fixed layer 102. The electrical current may flow asindicated by the arrows 120, 130, 140, and 150. In an embodiment where afourth sidewall (not shown) is included, electrical current may alsoflow as indicated by the arrow 160.

In a particular illustrative embodiment, the free layer 106 may carrymultiple independent magnetic domains, each of which may beindependently configured by a write current to orient a direction of amagnetic field within the free layer 106 relative to a fixed magneticfield associated with the fixed layer 102 to represent a data value. Inparticular, when a direction (orientation) of a magnetic field of thefixed layer 102 and the direction of the magnetic field of the freelayer 106 are aligned, a data value of “0” is represented. In contrast,when a direction (orientation) of the magnetic field of the free layer106 is opposite to the direction of the magnetic field of the fixedlayer 102, a data value of “1” is represented.

In a particular embodiment, a magnetic domain represents a physicalregion of magnetic material that carries a magnetic field having alargely homogenous or isotropic orientation. An interface between twomagnetic domains may be called a domain wall. The fixed layer 102 mayhave multiple fixed magnetic domains and associated domain walls thatare “pinned” (i.e., fixed during fabrication by application of anexternal magnetic field during a magnetic annealing process) by ananti-ferromagnetic (AFM) layer (not shown).

In a particular embodiment, each of the vertical portions of the freelayer 106 that is substantially parallel to a sidewall includes adistinct vertical magnetic domain. Each vertical magnetic domainincludes an independent magnetic field that oriented in a verticaldirection substantially parallel to a side wall or substantially normalto the bottom wall, and having a field direction toward the bottom wall116 (i.e., downward, in the direction of the arrow 150) or away from thebottom wall 116 (i.e., upward, opposite the direction of the arrow 150).A direction of a magnetic field of a vertical magnetic domain associatedwith the free layer 106 that is adjacent to the sidewall 110 mayrepresent a first data value. A direction of a magnetic field of avertical magnetic domain associated with the free layer 106 that isadjacent to the sidewall 112 may represent a second data value. Adirection of a magnetic field of a vertical magnetic domain associatedwith the free layer 106 that is adjacent to the sidewall 114 mayrepresent a third data value. In addition, a direction of a magneticfield of a horizontal magnetic domain associated with the free layer 106that is adjacent to the bottom wall 116 may represent a fourth datavalue.

FIG. 2 is a cross-sectional view of a magnetic tunnel junction (MTJ)cell 200 including multiple vertical magnetic domains that is adapted tostore multiple digital values. The MTJ cell 200 includes a bottomelectrode layer 202, a magnetic tunnel junction (MTJ) stack 204, and atop electrode layer 206. The MTJ stack 204 includes a free magneticlayer 208 that carries a magnetic field, which may be programmed byapplying a write current between the top electrode 206 and bottomelectrode 202. The MTJ stack 204 also includes a tunnel junction barrierlayer 210 and a fixed magnetic layer 212.

In a particular embodiment, the fixed layer 212 is generally annealed tobe pinned by an anti-ferromagnetic (AFM) layer (not shown) to fix adirection of a magnetic field that is carried by the fixed layer 212.The tunnel barrier 210 may be an oxide barrier layer (e.g., MgO, Al₂O₃,etc,) or other diamagnetic layer that is adapted to provide a tunneljunction or barrier between the fixed layer 212 and the free layer 208.The free layer 208 is formed from a ferromagnetic material that carriesa programmable (writeable) magnetic domain, which can be altered tostore a data value (i.e., a “1” or a “0” data value).

In a particular embodiment, the free layer 208 of the MTJ stack 204 maybe adapted to carry multiple independent magnetic domains. For example,the free layer 208 at a first sidewall 214 may include a first verticalmagnetic domain associated with a first data value. The free layer 208at a second sidewall 216 may include a second vertical magnetic domainassociated with a second data value. The free layer 208 at a bottom wall218 may include a horizontal magnetic domain associated with a thirddata value. The particular orientation of the magnetic field within thefree layer at the sidewalls 214 and 216 and at the bottom wall 218 maybe controlled, in part, by controlling length, width, and depthdimensions of the MTJ cell 200. In a particular embodiment, a magneticfield in a vertical magnetic domain (e.g., at the free layer 208 alongthe sidewall 214 or 216) orients in a vertical direction (i.e., downwardtoward the bottom wall 218 or upward away from the bottom wall 218)along a length of a wall of the MTJ cell 200.

FIG. 3 is a top view of a particular illustrative embodiment of a memorydevice 300 including a substrate 302 with a magnetic tunnel junction(MTJ) cell 304 with multiple vertical magnetic domains. The MTJ cell 304includes a first sidewall 306, a second sidewall 308, a third sidewall310, and a fourth sidewall 312 arranged in a substantially rectangularshape. The device 300 also includes electrical terminals, such as afirst terminal 328 and a second terminal 332 to access the MTJ cell 304.The device 300 also includes a third terminal 322 to couple to anelectrode 327 of the MTJ cell 304.

Each of the sidewalls 306, 308, 310, and 312 may include a fixed layer,a tunnel barrier, and a free layer, and an anti-ferromagnetic (AFM)layer. In a particular embodiment, each of the sidewalls 306, 308, 310,and 312 may include additional layers. The fixed layer is generallyannealed to be pinned by an anti-ferromagnetic layer to fix a directionof a magnetic domain that is carried by the fixed layer. The tunnelbarrier may be an oxide barrier layer (i.e., MgO, Al₂O₃, etc,) or otherdiamagnetic layer that is adapted to provide a tunnel junction orbarrier between the fixed layer and the free layer. The free layer isformed from a ferromagnetic material that carries a programmable(writeable) magnetic domain, which can be altered to store a data value(i.e., a “1” or a “0” data value). For example, the sidewall 310 carriesa first vertical magnetic domain 318. The sidewall 312 carries a secondvertical magnetic domain 320. The field direction symbols (.) and (*)indicate possible directions of a magnetic field in the domain (out ofthe page and into the page, respectively). In a particular embodiment,the first sidewall 306 and the second sidewall 308 also include verticalmagnetic domains. The terminal 322 is coupled to the electrode 327,which includes a center component 326 (depicted in FIG. 4) that extendsproximate to each of the sidewalls 306, 308, 310, and 312. The centercomponent 326 is spaced approximately equally from a second electrode321 that is adjacent to each of the sidewalls 306, 308, 310, and 312.

FIG. 4 is a cross-sectional view of the memory device of FIG. 3 takenalong line 4-4 in FIG. 3. The cross-sectional view 400 shows thesubstrate 302 including the magnetic tunnel junction (MTJ) cell 304. Inthis view, the cross-section is taken lengthwise through the MTJ cell304. The terminal 322 extends from a top surface 401 (i.e., a planarsurface) of the substrate 302 to the electrode 327. The terminals 328and 332 extend from the top surface 401 of the substrate 302 to thesecond electrode 321. The electrode 327 includes the center component326 that is proximate to each of the sidewalls 310 and 312 and that isspaced approximately equally from a bottom electrode 321 along each ofthe sidewalls 310 and 312 and a bottom wall 402. The MTJ cell 304includes a magnetic tunnel junction (MTJ) stack 406 and capping layers408 and 410. The MTJ stack 406 includes the sidewalls 310 and 312, whichare adapted to carry unique vertical magnetic domains representingstored digital values. The MTJ stack 406 is located in a trench havingdepth (d).

The electrode 321 extends along the bottom wall 402 of the MTJ cell 304and also extends along the sidewalls 310 and 312. The MTJ stack 406carries multiple unique vertical magnetic domains. The sidewall portion310 of the MTJ stack 406 carries a magnetic domain that includes themagnetic field 318, which extends along a height (a) of the sidewalls310 and 312 (i.e., along the surface of the page). In general, if aheight (a) of a sidewall 310 or 312 is greater than a width (c) of thesidewall, a magnetic field 318 or 320 carried by the sidewall 310 or 312of the MTJ stack 406 is oriented vertically along the respectivesidewall. Hence, in the cross-sectional view 400, the magnetic field 318extends along the surface of the page in a direction corresponding tothe height (a) of the sidewall 310. The direction of the magnetic field318 is determined by the stored data value. For example, a “1” value maybe represented by the magnetic field 318 extending down toward thebottom wall 402, while a “0” value may be represented by the magneticfield 318 extending up toward the electrode 327.

The MTJ stack 406 that is proximate to the bottom wall 402 carriesanother unique magnetic domain 404, which extends in a longitudinaldirection (i.e., along the direction (c) in FIG. 3 and normal to thepage in FIG. 4) along the bottom wall 402 of the MTJ cell 304. Since alength (c) of the bottom wall 402 is greater than a width (b) of thebottom wall 402, the magnetic domain 404 is oriented in a direction ofthe length (c).

In a particular embodiment, the MTJ cell 304 includes a width (b) and(c) that is less than sidewall height (a), which is approximately equalto the depth (d). The bottom wall 402 has a length (c) that is greaterthan a width (b). Accordingly, the magnetic domain 404 along the bottomwall 402 of the MTJ cell 304 is oriented along the length (c), and themagnetic domains 318 and 320 at the sidewalls 310 and 312 are orientedin a vertical direction along a length of the sidewalls 310 and 312(i.e., in a direction parallel to the dimension arrow (a) illustrated inFIG. 4).

Referring to FIG. 5, a cross-sectional view of a second particularillustrative embodiment of a memory device including a magnetic tunneljunction (MTJ) cell with multiple vertical magnetic domains is depictedand generally designated 500. The view 500 includes a substrate 502having a MTJ cell 504. Terminals 532 and 528 are coupled to a bottomelectrode 513. A terminal 522 extends from a top surface 501 of thesubstrate 502 and is coupled to an electrode 527 that includes a centercomponent 526. The center component 526 extends proximate to sidewalls510 and 512 of an MTJ stack 506. The center component 526 isapproximately equally spaced apart from the sidewalls 510 and 512 andfrom a bottom wall 515. The MTJ cell 504 also includes capping layers517 and 519 and the MTJ stack 506. The MTJ stack 506 includes at least afixed layer, a tunnel barrier, and a free layer, which carries multipleunique magnetic domains. In a particular embodiment, additional layers(AFM or other layers) may also be included between the top and bottomelectrodes 527 and 513.

For example, the MTJ stack 506 carries a first unique vertical magneticdomain at the sidewall 510, which includes the magnetic field 518. TheMTJ stack 506 also carries a second unique vertical magnetic domain atthe sidewall 512, which includes the magnetic field 520. The MTJ stack506 also carries a horizontal magnetic domain at the bottom wall 515,which includes the magnetic field 524. The multiple unique verticalmagnetic domains are enabled by relative dimensions of the sidewalls,with a sidewall width (such as (b)) less than a sidewall height (a),which is approximately equal to a trench depth (d). Each of the magneticfields 518, 520, and 524 may be programmed to have one of the tworespective directions indicated for the respective field. For example,the vertical fields 518 and 520 may be independently programmed to havea direction indicated by the upper arrowhead or a direction indicated bythe bottom arrowhead. Similarly, the horizontal field 524 may beprogrammed to have a direction into the page (indicated by “*”) or outof the page (indicated by “.”).

Referring to FIG. 6, a cross-sectional view of a third particularillustrative embodiment of a memory device including a magnetic tunneljunction (MTJ) cell with multiple vertical magnetic domains is depictedand generally designated 600. The view 600 includes a substrate 602having a MTJ cell 604. Terminals 632 and 628 are coupled to a bottomelectrode 613 and extend from a top surface 601. A terminal 623 iscoupled to the bottom electrode 613 and extends downward from the bottomelectrode 613. A terminal 622 extends from the top surface 601 of thesubstrate 602 and is coupled to an electrode 627 that includes a centercomponent 626. The center component 626 extends proximate to sidewalls610 and 612 of an MTJ stack 606. The center component 626 isapproximately equally spaced apart from the sidewalls 610 and 612 andfrom a bottom wall 615. The MTJ cell 604 also includes capping layers617 and 619 and the MTJ stack 606. The MTJ stack 606 includes a fixedlayer, a tunnel barrier, and a free layer, which carries multiple uniquemagnetic domains. The MTJ stack 606 may also include ananti-ferromagnetic layer, other layers, or any combination thereof.

For example, the MTJ stack 606 carries a first unique vertical magneticdomain at the sidewall 610, which includes the magnetic field 618. TheMTJ stack 606 also carries a second unique vertical magnetic domain atthe sidewall 612, which includes the magnetic field 620. The MTJ stackalso carries a horizontal magnetic domain at the bottom wall 615, whichincludes the magnetic field 624. The multiple unique vertical magneticdomains are enabled by relative dimensions of the sidewalls, with asidewall width (such as (b)) less than a sidewall height (a), which isapproximately equal to a trench depth (d). Each of the magnetic fields618, 620, and 624 may be programmed to have one of the two respectivedirections indicated for the respective field. For example, the verticalfields 618 and 620 may be independently programmed to have a directionindicated by the upper arrowhead or a direction indicated by the bottomarrowhead. Similarly, the horizontal field 624 may be programmed to havea direction into the page (indicated by “*”) or out of the page(indicated by “.”).

In a particular embodiment, one or more of the terminals 628, 632, and623 that are coupled to the bottom electrode 613 may be used todetermine a value stored via magnetic domains at each of the sidewalls610 and 612 as well as the bottom wall 615. For example, a current flowfrom the terminal 622 to the terminal 628 is primarily responsive to adirection of the magnetic field 618 relative to a fixed field associatedwith the sidewall 610. Likewise, a current flow from the terminal 622 tothe terminal 632 is primarily responsive to a direction of the magneticfield 620 relative to a fixed field associated with the sidewall 612. Acurrent flow from the terminal 622 to the terminal 623 is primarilyresponsive to a direction of the magnetic field 624 relative to a fixedfield associated with the bottom wall 615.

FIG. 7 is a top view of a particular illustrative embodiment of amagnetic tunnel junction (MTJ) stack with multiple vertical magneticdomains where the MTJ cell is written in a bit zero state. In thisexample, the MTJ stack 700 is illustrated in a bit zero state, whereeach of the bits represents a zero value. The MTJ stack 700 includes afirst sidewall 702, a second sidewall 704, a third sidewall 706, afourth sidewall 708, and a bottom wall 710. Each of the sidewalls 702,704, 706, and 708, and the bottom wall 710 include a fixed layer, atunnel barrier, and a free layer. The free layers of each of thesidewalls 702, 704, 706 and 708 carry unique vertical magnetic domainsand the free layer of the bottom wall 710 carries a unique magneticdomain configured to represent a data value, such as a “1” or a “0”value. The first sidewall 702 includes a free layer that carries avertical first magnetic domain 712. The second sidewall 704 includes afree layer that carries a vertical second magnetic domain 714. The thirdsidewall 706 includes a free layer that carries a vertical thirdmagnetic domain 716. The fourth sidewall 708 includes a free layer thatcarries a vertical fourth magnetic domain 718. The bottom wall 710includes a free layer that carries a horizontal fifth magnetic domain720.

The first magnetic domain 712 of the first sidewall 702 is separatedfrom the second magnetic domain 714 of the second sidewall 704 by afirst domain barrier 732. Similarly, the second magnetic domain 714 ofthe second sidewall 704 is separated from the third magnetic domain 716of the third sidewall 706 by a second domain barrier 734. The thirdmagnetic domain 716 of the third sidewall 706 is also separated from thefourth magnetic domain 718 of the fourth sidewall 708 by a third domainbarrier 736. The fourth magnetic domain 718 of the fourth sidewall 708is separated from the first magnetic domain 712 of the first sidewall702 by a fourth domain barrier 738.

In general, the first domain barrier 732, the second domain barrier 734,the third domain barrier 736 and the fourth domain barrier 738 representdomain walls, which are interfaces that separate magnetic domains, suchas the magnetic domains 712, 714, 716, and 718, respectively. Suchdomain barriers 732, 734, 736, and 738 represent a transition betweendifferent magnetic moments. In a particular embodiment, the domainbarriers 732, 734, 736, and 738 may represent a change in a magneticmoment where a magnetic field undergoes an angular displacement of 0 or180 degrees.

The direction of a magnetic field associated with the first magneticdomain 712 (i.e., a direction of a magnetic field within a free layer)in the first sidewall 702 may be altered using a first write current722. Similarly, a direction of a magnetic field associated with thesecond magnetic domain 714 carried by a free layer of the sidewall 704may be altered using a second write current 724. A direction of amagnetic field associated with the third magnetic domain 716 that iscarried by a free layer in the third sidewall 706 may be altered using athird write current 726. A direction of a magnetic field associated withthe fourth magnetic domain 718 carried by a free layer of the fourthsidewall 708 may be altered using a fourth write current 728. Adirection of a magnetic field associated with the fifth magnetic domain720 carried by a free layer of the bottom wall 710 may be altered usinga fifth write current 730.

In general, a relative direction of the magnetic field carried by thefree layer relative to a fixed magnetic field in the fixed layer of eachof the sidewalls 702, 704, 706, and 708 determines the bit value storedby that particular sidewall. In the example shown, the fixed layer andfree layer magnetic directions are in parallel (as illustrated in bymagnetic fields 814 and 816 in FIG. 8). Accordingly, the write currents722, 724, 726, 728, and 730 may represent write “0” currents, placingthe MTJ stack 700 in a reset or “0” state.

FIG. 8 is a diagram of a particular illustrative embodiment of layers ofa magnetic tunnel junction (MTJ) stack 800 illustrating a write zerocurrent flow direction. The MTJ structure 800 includes a top electrode802, a free layer 804, a magnetic tunnel junction tunnel barrier 806, afixed layer 808, and a bottom electrode 810. An anti-ferromagnetic (AF)layer may be located between the fixed layer 808 and the bottomelectrode 810. In general, the top electrode 802 and the bottomelectrode 810 are electrically conductive layers adapted to carry anelectrical current. The fixed layer 808 is a ferromagnetic layer thathas been annealed to be pinned, such as by an AF layer, to fix adirection of a magnetic field 816 within the fixed layer 808. The freelayer 804 is a ferromagnetic layer that may be programmed by a writecurrent. The MTJ tunnel barrier or barrier layer 806 may be formed froman oxide barrier layer (i.e., MgO, Al₂O₃, etc,) or other diamagneticmaterial. The direction of a magnetic field 814 within the free layer804 may be changed using the write current. The MTJ stack 800 may alsoinclude a synthesis fixed layer structure, a synthesis free layer (SyF)structure, a dual spin filter (DSF) structure, or any combinationthereof.

A direction of the magnetic fields in the free layer 804 relative to thefixed magnetic field of the fixed layer 808 indicates whether the databit stored at the free layer 804 of the particular MTJ cell 800 is a bitvalue of “1” or bit value of “0.” The magnetic direction of the magneticfield in the free layer 804, generally indicated at 814, may be changedusing a write current 812. As shown, the write current represent a write0 current that flows from the top electrode 802 through the free layer804, across the magnetic tunnel junction barrier 806, through the fixedlayer 808, and through the bottom electrode 810.

FIG. 9 is a cross-sectional view 900 of the MTJ stack of FIG. 7 takenalong line 9-9 in FIG. 7. The MTJ stack includes the first sidewall 702,the third sidewall 706 and the bottom wall 710. In this example, adirection of a first magnetic field carried by the free layer in thefirst sidewall 702, as indicated at 712, extends vertically along thefirst sidewall 702 and in a direction corresponding to the arrow 712. Adirection of a third magnetic field carried by the free layer of thethird sidewall 706, as indicated at 716, extends vertically along thethird sidewall 706 and in a direction corresponding to the arrow 716.

The MTJ stack includes a first domain barrier (wall) 934 and a seconddomain barrier 936. In a particular example, the second domain barrier936 may correspond to a structural interface between the sidewall 702and the bottom wall 710. The second domain barrier 936 isolates thefirst magnetic domain 712 of the free layer of the first sidewall 702from the fifth magnetic domain 720 at the bottom wall 710. The MTJ stackalso includes a third domain barrier 938 and a fourth domain barrier940. The fourth domain barrier 940 may correspond to a structuralinterface between the bottom wall 710 and the sidewall 706. The fourthdomain barrier 940 isolates the magnetic field 716 of a free layer ofthe sidewall 706 from the magnetic field 720 of the free layerassociated with the bottom wall 710.

In the embodiment illustrated in FIG. 9, the MTJ stack may be adapted tostore at least three data bits. A first data bit may be represented bythe first magnetic field 712 carried by a free layer of the firstsidewall 702. A second data bit may be represented by the fifth magneticfield 720 carried by a free layer of the bottom wall 710. A third databit may be represented by the third magnetic field 716 carried by a freelayer of the third sidewall 706. The write currents 722, 726, and 730may be applied to selectively alter an orientation of the magnetic fieldof a selected sidewall without altering the orientation of the magneticfield associated with the other sidewall or of the bottom wall 710, forexample.

FIG. 10 is a cross-sectional view 1000 of the MTJ stack of FIG. 7 takenalong line 10-10 in FIG. 7. The MTJ stack illustrates the sidewalls 704and 708 of the MTJ stack. In this particular example, the MTJ stackincludes magnetic domains barriers 1004 and 1006. The magnetic domainbarrier (or wall) 1006 isolates the magnetic domain 718 carried by afree layer of the sidewall 708 from the magnetic domain 720 carried by afree layer of the bottom wall 710. Additionally, the MTJ stack includesthe magnetic domain barriers 1008 and 1010. The domain barrier 1010 maycorrespond to a structural interface between the sidewall 704 and thebottom wall 710. The domain barrier 1010 may isolate the magnetic field714 carried by the free layer of the sidewall 704 from the magneticfield 720 carried by the free layer of the bottom wall 710.

In a particular illustrative embodiment, the domain barriers 732, 734,736 and 738 illustrated in FIG. 7, the domain barriers 936 and 940illustrated in FIG. 9, and the domain barriers 1006 and 1010 illustratedin FIG. 10 enable the MTJ stack to store multiple digital values. Inparticular, the MTJ stack illustrated in FIG. 7 may be adapted to storeup to five digital values, which may be represented by the magneticfields 712, 714, 716, 718, and 720, illustrated in FIGS. 7, 9, and 10.The digital values represented by the magnetic fields 712, 714, 716,718, and 720 may represent up to thirty two logic states.

FIG. 11 is a top view of a magnetic tunnel junction (MTJ) stack 1100with multiple vertical magnetic domains where the MTJ stack is writtenin a bit one state, where each of the bits stored at the MTJ stack 1100has a logic high or “1” value. The MTJ stack 1100 includes sidewalls1102, 1104, 1106, and 1108, and a bottom wall 1110. Each of thesidewalls 1102, 1104, 1106, and 1108 and the bottom wall 1110 include afixed layer, a tunnel barrier, and a free layer. Each of the sidewalls1102, 1104, 1106 and 1108 and the bottom wall 1110 carries a uniquemagnetic domain. The first sidewall 1102 includes a free layer thatcarries a vertical first magnetic domain 1112. The second sidewall 1104includes a free layer that carries a vertical second magnetic domain1114. The third sidewall 1106 includes a free layer that carries avertical third magnetic domain 1116. The fourth sidewall 1108 includes afree layer that carries a vertical fourth magnetic domain 1118. Thebottom wall 1110 includes a free layer that carries a horizontal fifthmagnetic domain 1120. The MTJ stack 1100 may also include a synthesisfixed layer structure, a synthesis free layer (SyF) structure, a dualspin filter (DSF) structure, or any combination thereof.

The first magnetic domain 1112 of the first sidewall 1102 is separatedfrom the second magnetic domain 1114 of the second sidewall 1104 by afirst domain barrier 1132. Similarly, the second magnetic domain 1114 ofthe second sidewall 1104 is separated from the third magnetic domain1116 of the third sidewall 1106 by a second domain barrier 1134. Thethird magnetic domain 1116 of the third sidewall 1106 is separated fromthe fourth magnetic domain 1118 of the fourth sidewall 1108 by a thirddomain barrier 1136. The fourth magnetic domain 1118 of the fourthsidewall 1108 is separated from the first magnetic domain 1112 of thefirst sidewall 1102 by a fourth domain barrier 1138.

A direction of orientation of a magnetic field associated with the firstmagnetic domain 1112 at a free layer of the first sidewall 1102 may bealtered using a write current 1122. Similarly, a direction oforientation of a magnetic field associated with the second magneticdomain 1114 in the second sidewall 1104 may be altered using a writecurrent 1124. A direction of orientation of a magnetic field associatedwith the third magnetic domain 1116 carried by the free layer in thethird sidewall 1106 may be altered using a write current 1126. Adirection of orientation of a magnetic field associated with the fourthmagnetic domain 1118 in the fourth sidewall 1108 may be altered using awrite current 1128. A direction of a magnetic field associated with thefifth magnetic domain 1120 in the bottom wall 1110 may be altered usinga write current 1130.

In general, a relative direction of the magnetic field of the firstmagnetic domain 1112 carried by the free layer relative to a directionof orientation of a fixed magnetic field in the fixed layer of each ofthe sidewalls 1102, 1104, 1106, and 1108 determines the bit value storedby that particular sidewall. In the example shown, the fixed layer andfree layer magnetic directions are in an anti-parallel relationship.Each of the write currents 1122, 1124, 1126 and 1128 may represent write“1” currents, which can be used to selectively orient a direction of themagnetic fields of the vertical magnetic domains 1112, 1114, 1116, 1118to represent a value of “1” at each of the sidewalls 1102, 1104, 1106,and 1108, respectively. Additionally, the write current 1130 mayrepresent a write “1” current, which can be used to selectively orientthe magnetic field of the horizontal fifth magnetic domain 1120 at thebottom wall 1110.

FIG. 12 is a diagram of a particular illustrative embodiment of layersof a magnetic tunnel junction (MTJ) structure illustrating a write onecurrent flow direction. A MTJ stack 1200 includes a top electrode 1202,a free layer 1204, a magnetic tunnel junction tunnel barrier 1206, afixed layer 1208, and a bottom electrode 1210. An anti-ferromagnetic(AF) layer (not shown) may be located between the fixed layer 1208 andthe bottom electrode 1210. In general, the top electrode 1202 and thebottom electrode 1210 are electrically conductive layers adapted tocarry an electrical current. The fixed layer 1208 is a ferromagneticlayer that has been annealed, such as to be pinned by ananti-ferromagnetic layer, to fix a direction of a magnetic field 1216within the fixed layer 1208. The free layer 1204 is also a ferromagneticlayer that may be programmed by write current. The MTJ tunnel barrier orbarrier layer 1206 may be formed from an oxide barrier layer (i.e., MgO,Al₂O₃, etc,) or other diamagnetic material. The direction of a magneticfield 1214 within the free layer 1204 may be changed using a writecurrent 1212.

A direction of the magnetic field 1214 carried by the free layer 1204relative to the fixed magnetic field 1216 of the fixed layer 1208indicates whether the data bit stored in the particular MTJ stack 1200is a bit value of “1” or bit value of “0.” In this example, the magneticfield 1214 within the free layer 1204 is oriented in a direction that isopposite a direction of the magnetic field 1216 within the fixed layer1208, representing a data value of “1”. The direction of the magneticfield 1214 in the free layer 1204 may be changed using the write current1212. As shown, the write current represent a write “1” current thatflows from the bottom electrode 1210 through the fixed layer 1208 acrossthe magnetic tunnel junction barrier 1206 through the free layer 1204and through the top electrode 1202.

FIG. 13 is a cross-sectional view 1300 of the MTJ stack 1100 of FIG. 11taken along line 13-13 in FIG. 11. The MTJ stack 1100 includes thesidewalls 1102 and 1106 and the bottom wall 1110. In this example, adirection of a magnetic field that is carried by the free layer in thefirst sidewall 1102, as indicated at 1112, extends as indicated by thearrow 1112 illustrated in FIG. 13. In the particular cross-sectionalview of FIG. 13, the magnetic field 1112 extends along the page and in adirection toward the bottom wall 1110. The magnetic field 1116 carriedby the free layer of the third sidewall 1106 extends along the page andin a direction toward the bottom wall 1110.

The MTJ stack 1100 includes a first domain barrier 1334 and a seconddomain barrier 1336. In a particular example, the second domain barrier1336 may correspond to a structural interface between the first sidewall1102 and the bottom wall 1110. The second domain barrier 1336 isolatesthe first magnetic domain 1112 of the free layer of the first sidewall1102 from the fifth magnetic domain 1120 of the bottom wall 1110. TheMTJ stack 1100 also includes a domain barrier 1338 and a domain barrier1340. The domain barrier 1340 may correspond to a structural interfacebetween the bottom wall 1110 and the third sidewall 1106. The domainbarrier 1340 isolates a magnetic field 1116 of the free layer of thesidewall 1106 from the magnetic field 1120 of the free layer associatedwith the bottom wall 1110.

In the embodiment illustrated in FIG. 13, the MTJ stack 1100 may beconfigured to store at least three digital values. A first digitalvalue, such as a data bit, may be represented by the magnetic field 1112carried by the free layer of the sidewall 1102. A second digital valuemay be represented by the magnetic field 1120 carried by the free layerof the bottom wall 1110. A third digital value may be represented by themagnetic field 1116 carried by the free layer of the sidewall 1106. In aparticular example, a data bit having a “1” value or a logic high valuemay be written to the magnetic domains of the vertical sidewalls 1102and 1106 and to the magnetic domain of the horizontal bottom wall 1110via write currents 1122, 1126, and 1130, respectively. The writecurrents 1122, 1126, and 1130 may be applied to selectively alter anorientation of the magnetic field (e.g., the magnetic field 1112) of aselected sidewall (e.g., the first sidewall 1102) without altering theorientation of the magnetic field (e.g., the magnetic field 1116)associated with the other sidewall (e.g. the sidewall 1106) and withoutaltering the orientation of the magnetic field 1120 of the bottom wall1110. Similarly, the orientation of the magnetic fields 1120 and 1116may be altered independently.

FIG. 14 is a cross-sectional view of the MTJ stack 1100 of FIG. 11 takenalong line 14-14 in FIG. 11. The MTJ stack 1100 includes the sidewalls1108 and 1104. In this particular example, the MTJ stack 1100 includesthe magnetic domains barriers 1404 and 1406. The magnetic domain barrier(or wall) 1406 isolates the magnetic domain 1118 carried by the freelayer of the sidewall 1108 from the magnetic domain 1120 carried by thefree layer of the bottom wall 1110. Additionally, the MTJ stack 1100includes the magnetic domain barriers 1408 and 1410. The domain barrier1410 may correspond to a structural interface between the sidewall 1104and the bottom wall 1110. The domain barrier 1410 isolates the magneticfield 1114 carried by the free layer of the sidewall 1104 from themagnetic field 1120 carried by the free layer of the bottom wall 1110.The write currents 1128, 1130, and 1124 may be used to alter anorientation of the magnetic fields 1118, 1120, and 1114, respectively.In a particular embodiment, the write currents 1128, 1130 and 1124 maybe applied independently to selectively alter a magnetic orientation ofa magnetic field associated with a selected sidewall (e.g., the magneticfield 1118 of the sidewall 1108) without altering a magnetic orientationassociated with the magnetic fields of the sidewall 1104 or the bottomwall 1110 (i.e., the magnetic fields 1114 and 1120, respectively).

FIG. 15 is a top view of a fourth illustrative embodiment of a memorydevice including a magnetic tunnel junction (MTJ) cell with multiplevertical magnetic domains. The memory device 1500 includes a substrate1502 with a magnetic tunnel junction (MTJ) cell 1504 with multiplevertical magnetic domains. Sidewall material under a mask area 1550 hasbeen removed to remove a first sidewall 1506 of the MTJ cell 1504. TheMTJ cell 1504 includes a second sidewall 1508, a third sidewall 1510,and a fourth sidewall 1512 arranged in a substantially U-shape. Thedevice 1500 also includes electrical terminals, such as a first terminal1528, a second terminal 1532, and a third terminal 1552 to access theMTJ cell 1504. A fourth terminal 1522 is coupled to an electrode 1527 ofthe MTJ cell 1504. The terminals 1528, 1532, 1552, and 1522 are coupledto wires 1560, 1562, 1564, and 1566, respectively.

Each of the sidewalls 1508, 1510, and 1512 includes a fixed layer, atunnel barrier, and a free layer. Additional layers, such as ananti-ferromagntic (AF) layer, may be included. The fixed layer isgenerally annealed, such as to be pinned by an AF layer, to fix adirection of a magnetic domain that is carried by the fixed layer. Thetunnel barrier may be an oxide barrier layer (i.e., MgO, Al₂O₃, etc,) orother diamagnetic layer that is adapted to provide a tunnel junction orbarrier between the fixed layer and the free layer. The free layer isformed from a ferromagnetic material that carries a programmable(writeable) magnetic domain, which can be altered to store a data value(i.e., a “1” or a “0” data value). The sidewall 1508 carries a verticalmagnetic domain 1554 that is accessible via the terminal 1552. Thesidewall 1510 carries a vertical magnetic domain 1518 that is accessiblevia the terminal 1528. The sidewall 1512 carries a vertical magneticdomain 1520 that is accessible via the terminal 1532. The fielddirection symbols (.) and (*) indicate possible directions of a magneticfield in the domain (out of the page and into the page, respectively).The terminal 1522 is coupled to the electrode 1527, which includes acenter component 1526 (depicted in FIG. 16) that extends proximate toeach of the sidewalls 1508, 1510, and 1512.

FIG. 16 is a cross-sectional view of the memory device of FIG. 15 takenalong line 16-16 in FIG. 15. The cross-sectional view 1600 shows thesubstrate 1502 including the magnetic tunnel junction (MTJ) cell 1504.In this view, the cross-section is taken lengthwise through the MTJ cell1504. The electrode 1527 includes the center component 1526 that isproximate to each of the sidewalls 1510 and 1512 and that is spacedapproximately equally from a bottom electrode 1670 along each of thesidewalls 1510 and 1512 and a bottom wall 1672. The MTJ cell 1504includes a magnetic tunnel junction (MTJ) stack 1680 and capping layers1682, 1684, and 1686. The MTJ stack 1680 includes the sidewalls 1510 and1512, which are adapted to carry unique vertical magnetic domainsrepresenting stored digital values. The MTJ stack 1680 is located in atrench having depth (d).

The bottom electrode 1670 extends along the bottom wall 1672 of the MTJcell 1504 and also extends along the sidewalls 1510 and 1512. The MTJstack 1680 carries multiple unique vertical magnetic domains 1518, 1520,and 1554 along a vertical height (a) of the sidewalls 1510, 1512, and1508, respectively. In a particular embodiment, the MTJ cell 1504includes lateral dimensions (b) and (c) that are less than sidewallheight (a), which is approximately equal to the trench depth (d).

In general, when a height (a) of a sidewall 1508, 1510, or 1512 isgreater than a width (b) or (c) of the sidewall, a magnetic field withinthe sidewall aligns to a longitudinal sidewall direction orientedvertically along the height (a). In a particular embodiment, by removingthe first sidewall 1506, MTJ device 1500, in which magnetic fields inthe vertical sidewalls are oriented vertically.

The MTJ stack 1680 that is proximate to the bottom wall 1672 carriesanother unique magnetic domain 1674, which extends in a longitudinaldirection (i.e., along the direction (c) in FIG. 15 and normal to thepage in FIG. 16). Because a length (c) of the bottom wall 1672 isgreater than a width (b) of the bottom wall 1672, the magnetic domain1674 is oriented in a direction of the length (c).

FIG. 17 is a top view of a fifth illustrative embodiment of a memorydevice including a magnetic tunnel junction (MTJ) cell with multiplevertical magnetic domains. The memory device 1700 includes a substrate1702 with a magnetic tunnel junction (MTJ) cell 1704 with multiplevertical magnetic domains. Sidewall material under a mask area 1750 hasbeen removed to remove a first sidewall 1706 of the MTJ cell. The MTJcell 1704 includes a second sidewall 1708, a third sidewall 1710, and afourth sidewall 1712 arranged in a substantially U-shape. The device1700 also includes electrical terminals, such as a first terminal 1728,a second terminal 1732, and a third terminal 1752 to access the MTJ cell1704. The device 1700 also includes a fourth terminal 1722 to couple toan electrode 1727 of the MTJ cell 1704. The terminals 1728, 1732, and1752 are coupled to bottom wires 1760, 1762, and 1764, respectively, andthe terminal 1722 is coupled to a top wire 1766.

Each of the sidewalls 1708, 1710, and 1712 includes a fixed layer, atunnel barrier, and a free layer. The fixed layer is generally annealedto be pinned by an anti-ferromagnetic film layer (not shown) to fix adirection of a magnetic domain that is carried by the fixed layer. Thetunnel barrier may be an oxide barrier layer (i.e., MgO, Al₂O₃, etc,) orother diamagnetic layer that is adapted to provide a tunnel junction orbarrier between the fixed layer and the free layer. The free layer isformed from a ferromagnetic material that carries a programmable(writeable) magnetic domain, which can be altered to store a data value(i.e., a “1” or a “0” data value). The sidewall 1708 carries a verticalmagnetic domain 1754 that is accessible via the terminal 1752. Thesidewall 1710 carries a vertical magnetic domain 1718 that is accessiblevia the terminal 1728. The sidewall 1712 carries a vertical magneticdomain 1720 that is accessible via the terminal 1732. The fielddirection symbols (.) and (*) indicate possible directions of a magneticfield in the domain (out of the page and into the page, respectively).The terminal 1722 is coupled to the electrode 1727, which includes acenter component 1726 (depicted in FIG. 18) that extends proximate toeach of the sidewalls 1708, 1710, and 1712.

FIG. 18 is a cross-sectional view of the memory device of FIG. 17 takenalong line 18-18 in FIG. 17. The cross-sectional view 1800 shows thesubstrate 1702 including the magnetic tunnel junction (MTJ) cell 1704.In this view, the cross-section is taken lengthwise through the MTJ cell1704. The electrode 1727 includes the center component 1726 that isproximate to each of the sidewalls 1710 and 1712 and that is spacedapproximately equally from a bottom electrode 1870 along each of thesidewalls 1710 and 1712 and a bottom wall 1872. The MTJ cell 1704includes a magnetic tunnel junction (MTJ) stack 1880 and capping layers1882, 1884, and 1886. The MTJ stack 1880 includes the sidewalls 1710 and1712, which are adapted to carry unique vertical magnetic domainsrepresenting stored digital values. The MTJ stack 1880 is located in atrench having depth (d).

The bottom electrode 1870 extends along the bottom wall 1872 of the MTJcell 1704 and also extends along the sidewalls 1710 and 1712. The MTJstack 1880 carries multiple unique vertical magnetic domains 1718, 1720,and 1754 along a vertical height (a) of the sidewalls 1710, 1712, and1708, respectively. In a particular embodiment, the MTJ cell 1704includes lateral dimensions (b) and (c) that are less than sidewallheight (a), which is approximately equal to the trench depth (d).

In general, when a height (a) of a sidewall 1708, 1710, or 1712 isgreater than a width (b) or (c) of the sidewall, a magnetic field withinthe sidewall is oriented vertically along the height (a). In aparticular embodiment, by removing the first sidewall 1706, MTJ device1700, in which magnetic fields in the vertical sidewalls are orientedvertically.

The MTJ stack 1880 that is proximate to the bottom wall 1872 carriesanother unique magnetic domain 1874, which extends in a longitudinaldirection (i.e., along the direction (c) in FIG. 17 and normal to thepage in FIG. 18). Because a length (c) of the bottom wall 1872 isgreater than a width (b) of the bottom wall 1872, the magnetic domain1874 is oriented in a direction of the length (c).

FIG. 19 is a top view of a sixth illustrative embodiment of a memorydevice including a magnetic tunnel junction (MTJ) cell with multiplevertical magnetic domains. The memory device 1900 includes a substrate1902 with a magnetic tunnel junction (MTJ) cell 1904 that has multiplevertical magnetic domains and a horizontal magnetic domain. Sidewallmaterial under a mask area 1950 has been removed to remove a firstsidewall 1906 of the MTJ cell. The MTJ cell 1904 includes a secondsidewall 1908, a third sidewall 1910, and a fourth sidewall 1912arranged in a substantially U-shape. The device 1900 also includeselectrical terminals, such as a first terminal 1928, a second terminal1932, a third terminal 1952, and a fourth terminal 2090 (depicted inFIG. 20) to access the MTJ cell 1904. The device 1900 also includes afifth terminal 1922 to couple to an electrode 1927 of the MTJ cell 1904.The terminals 1928, 1932, 1952, and 1922 are coupled to top wires 1960,1962, 1964, and 1966, respectively, and the terminal 2090 is coupled toa bottom wire 2092.

Each of the sidewalls 1908, 1910, and 1912 includes a fixed layer, atunnel barrier, and a free layer. The fixed layer is generally annealedto be pinned, such as by an anti-ferromagnetic film layer, to fix adirection of a magnetic domain that is carried by the fixed layer. Thetunnel barrier may be an oxide barrier layer (i.e., MgO, Al₂O₃, etc,) orother diamagnetic layer that is adapted to provide a tunnel junction orbarrier between the fixed layer and the free layer. The free layer isformed from a ferromagnetic material that carries a programmable(writeable) magnetic domain, which can be altered to store a data value(i.e., a “1” or a “0” data value). The sidewall 1908 carries a verticalmagnetic domain 1954 that is accessible via the terminal 1952. Thesidewall 1910 carries a vertical magnetic domain 1918 that is accessiblevia the terminal 1928. The sidewall 1912 carries a vertical magneticdomain 1920 that is accessible via the terminal 1932. The fielddirection symbols (.) and (*) indicate possible directions of a magneticfield in the domain (out of the page and into the page, respectively).The terminal 1922 is coupled to the electrode 1927, which includes acenter component 1926 (depicted in FIG. 20) that extends proximate toeach of the sidewalls 1908, 1910, and 1912.

FIG. 20 is a cross-sectional view of the memory device of FIG. 19 takenalong line 20-20 in FIG. 19. The cross-sectional view 2000 shows thesubstrate 1902 including the magnetic tunnel junction (MTJ) cell 1904.In this view, the cross-section is taken lengthwise through the MTJ cell1904. The electrode 1927 includes the center component 1926 that isproximate to each of the sidewalls 1910 and 1912 and that is spacedapproximately equally from a bottom electrode 2070 along each of thesidewalls 1910 and 1912 and a bottom wall 2072. The MTJ cell 1904includes a magnetic tunnel junction (MTJ) stack 2080 and capping layers2082, 2084, and 2086. The MTJ stack 2080 includes the sidewalls 1910 and1912, which are adapted to carry unique vertical magnetic domainsrepresenting stored digital values. The MTJ stack 2080 is located in atrench having depth (d).

The bottom electrode 2070 extends along the bottom wall 2072 of the MTJcell 1904 and also extends along the sidewalls 1910 and 1912. The MTJstack 2080 carries multiple unique vertical magnetic domains 1918, 1920,and 1954 along a vertical height (a) of the sidewalls 1910, 1912, and1908, respectively. In a particular embodiment, the MTJ cell 1904includes lateral dimensions (b) and (c) that are less than sidewallheight (a), which is approximately equal to the trench depth (d).

In general, when a height (a) of a sidewall 1908, 1910, or 1912 isgreater than a width (b) or (c) of the sidewall, a magnetic field withinthe sidewall is oriented vertically along the height (a). In aparticular embodiment, with the first sidewall 1906 removed, themagnetic fields in the vertical sidewalls of the MTJ device 1900 areoriented vertically.

The MTJ stack 2080 that is proximate to the bottom wall 2072 carriesanother unique magnetic domain 2074, which extends in a longitudinaldirection (i.e., along the direction (c) in FIG. 19 and normal to thepage in FIG. 20). Because a length (c) of the bottom wall 2072 isgreater than a width (b) of the bottom wall 2072, the magnetic domain2074 is oriented in a direction of the length (c).

Each magnetic domain of the MTJ device 1904 is independently accessible.For example, each of the vertical magnetic domains 1918, 1920, and 1954is accessible via a corresponding terminal 1928, 1932, and 1952,respectively. The horizontal magnetic domain 2074 is also accessible viathe bottom terminal 2090. Thus, data values may be read from or writtento each of the magnetic domains 1918, 1920, 1954, and 2074independently.

FIG. 21 is a top view of a seventh illustrative embodiment of a memorydevice including a magnetic tunnel junction (MTJ) cell with multiplevertical magnetic domains. The memory device 2100 includes a substrate2102 with a magnetic tunnel junction (MTJ) cell 2104 that has multiplevertical magnetic domains and a horizontal magnetic domain. Materialunder a mask area 2150 has been removed to remove a first sidewall 2106of the MTJ cell 2104. The MTJ cell 2104 includes a second sidewall 2108,a third sidewall 2110, and a fourth sidewall 2112 arranged in asubstantially U-shape. The device 2100 includes a first terminal 2290(depicted in FIG. 22) to access the MTJ cell 2104. The device 2100 alsoincludes a second terminal 2122 to couple to an electrode 2127 of theMTJ cell 2104. The terminal 2122 is coupled to a top wire 2166, and theterminal 2290 is coupled to a bottom wire 2292.

Each of the sidewalls 2108, 2110, and 2112 includes a fixed layer, atunnel barrier, and a free layer. The fixed layer is generally annealedto fix a direction of a magnetic domain that is carried by the fixedlayer. The tunnel barrier may be an oxide barrier layer (i.e., MgO,Al₂O₃, etc,) or other diamagnetic layer that is adapted to provide atunnel junction or barrier between the fixed layer and the free layer.The free layer is formed from a ferromagnetic material that carries aprogrammable (writeable) magnetic domain, which can be altered to storea data value (i.e., a “1” or a “0” data value). The sidewalls 2108,2110, and 2112 carry vertical magnetic domains 2154, 2118, and 2120,respectively. The field direction symbols (.) and (*) indicate possibledirections of a magnetic field in the domain (out of the page and intothe page, respectively). The terminal 2122 is coupled to the electrode2127, which includes a center component 2126 (depicted in FIG. 22) thatextends proximate to each of the sidewalls 2108, 2110, and 2112.

FIG. 22 is a cross-sectional view of the memory device of FIG. 21 takenalong line 22-22 in FIG. 21. The cross-sectional view 2200 shows thesubstrate 2102 including the magnetic tunnel junction (MTJ) cell 2104.In this view, the cross-section is taken lengthwise through the MTJ cell2104. The electrode 2127 includes the center component 2126 that isproximate to each of the sidewalls 2110 and 2112 and that is spacedapproximately equally from a bottom electrode 2270 along each of thesidewalls 2110 and 2112 and a bottom wall 2272. The MTJ cell 2104includes a magnetic tunnel junction (MTJ) stack 2280 and capping layers2282, 2284, and 2286. The MTJ stack 2280 is located in a trench havingdepth (d).

The bottom electrode 2270 extends along the bottom wall 2272 of the MTJcell 2104 and also extends along the sidewalls 2110 and 2112. The MTJstack 2280 carries multiple unique vertical magnetic domains 2118, 2120,and 2154 along a vertical height (a) of the sidewalls 2110, 2112, and2108, respectively. In a particular embodiment, the MTJ cell 2104includes lateral dimensions (b) and (c) that are less than sidewallheight (a), which is approximately equal to the trench depth (d).

In general, when a height (a) of a sidewall 2108, 2110, or 2112 isgreater than a width (b) or (c) of the sidewall, a magnetic field withinthe sidewall has oriented vertically along the height (a). In aparticular embodiment, with the first sidewall 2106 removed, themagnetic fields in the vertical sidewalls of the MTJ device 2100 areoriented vertically.

The MTJ stack 2280 that is proximate to the bottom wall 2272 carriesanother unique magnetic domain 2274, which extends in a longitudinaldirection (i.e., along the direction (c) in FIG. 21 and normal to thepage in FIG. 22). Because a length (c) of the bottom wall 2272 isgreater than a width (b) of the bottom wall 2272, the magnetic domain2274 is oriented in a direction of the length (c).

FIG. 23 is a top view of a second illustrative embodiment of a magnetictunnel junction (MTJ) stack with multiple vertical magnetic domainswhere the MTJ cell is written in a bit zero state. In this example, theMTJ stack 2300 is illustrated in a bit zero state, where each of thebits represents a zero value. The MTJ stack 2300 includes a firstsidewall 2302, a second sidewall 2306, a third sidewall 2308, and abottom wall 2558 (depicted in FIG. 25). A sidewall opposite the thirdsidewall 2308 has been removed to form a U-shaped structure. Each of thesidewalls 2302, 2306, and 2308 and the bottom wall 2558 may include afixed layer, a tunnel barrier, a free layer, and an anti-ferromagneticfilm (AF) layer, in addition to one or more additional layers. The freelayers of each of the sidewalls 2302, 2306, and 2308 carry uniquevertical magnetic domains and the free layer of the bottom wall 2558carries a unique magnetic domain configured to represent a data value,such as a “1” or a “0” value. The first sidewall 2302 includes a freelayer that carries a vertical first magnetic domain 2312. The secondsidewall 2306 includes a free layer that carries a vertical secondmagnetic domain 2316. The third sidewall 2308 includes a free layer thatcarries a vertical third magnetic domain 2318. The bottom wall 2558includes a free layer that carries a horizontal fourth magnetic domain2320.

The first magnetic domain 2312 of the first sidewall 2302 is separatedfrom the third magnetic domain 2318 of the third sidewall 2308 by afirst domain barrier 2338. The second magnetic domain 2316 of the secondsidewall 2306 is also separated from the third magnetic domain 2318 ofthe third sidewall 2308 by a second domain barrier 2336. In general, thedomain barriers 2336 and 2338 represent domain walls, which areinterfaces that separate magnetic domains, such as the magnetic domains2312, 2316, and 2318. Such domain barriers 2336 and 2338 represent atransition between different magnetic moments. In a particularembodiment, the domain barriers 2336 and 2338 may represent a change ina magnetic moment where a magnetic field undergoes an angulardisplacement of 0 or 180 degrees.

The direction of a magnetic field associated with the first magneticdomain 2312 (i.e., a direction of a magnetic field within a free layer)in the first sidewall 2302 may be altered using a first write current2322. A direction of a magnetic field associated with the secondmagnetic domain 2316 that is carried by a free layer in the secondsidewall 2306 may be altered using a second write current 2326. Adirection of a magnetic field associated with the third magnetic domain2318 carried by a free layer of the third sidewall 2308 may be alteredusing a third write current 2328. A direction of a magnetic fieldassociated with the fourth magnetic domain 2320 carried by a free layerof the bottom wall 2558 may be altered using a fourth write current2330.

In general, a relative direction of the magnetic field carried by thefree layer relative to a fixed magnetic field in the fixed layer of eachof the sidewalls 2302, 2306, 2308, and a bottom wall 2558 (depicted inFIG. 25) determines the bit value stored by that particular sidewall. Inthe example shown, the fixed layer and free layer magnetic directionsare in parallel (as illustrated in by magnetic fields 2414 and 2416 inFIG. 24). Accordingly, the write currents 2322, 2326, 2328, and 2330 mayrepresent write “0” currents, placing the MTJ stack 2300 in a reset or“0” state.

FIG. 24 is a diagram of a second illustrative embodiment of layers of amagnetic tunnel junction (MTJ) stack 2400 illustrating a write zerocurrent flow direction. The MTJ structure 2400 includes a top electrode2402, a free layer 2404, a magnetic tunnel junction tunnel barrier 2406,a fixed layer 2408, and a bottom electrode 2410. The MTJ stack 2400 mayalso include an anti-ferromagnetic (AF) layer (not shown) between thefixed layer 2408 and the bottom electrode 2410. In general, the topelectrode 2402 and the bottom electrode 2410 are electrically conductivelayers adapted to carry an electrical current. The fixed layer 2408 is aferromagnetic layer that has been annealed, such as to be pinned by ananti-ferromagnetic (AF) layer, to fix a direction of a magnetic field2416 within the fixed layer 2408. The free layer 2404 is a ferromagneticlayer that can be programmed via a write current. The MTJ tunnel barrieror barrier layer 2406 may be formed from an oxide barrier layer (i.e.,MgO, Al₂O₃, etc,) or other diamagnetic material. The direction of amagnetic field 2414 within the free layer 2404 may be changed using thewrite current. In a particular embodiment, the MTJ stack 2400 can alsoinclude a synthesis fixed layer structure, a synthesis free layer (SyF)structure, a dual spin filter (DSF) structure, or any combinationthereof.

A direction of the magnetic fields in the free layer 2404 relative tothe fixed magnetic field of the fixed layer 2408 indicates whether thedata bit stored at the free layer 2404 of the particular MTJ structure2400 is a bit value of “1” or bit value of “0.” The magnetic directionof the magnetic field in the free layer 2404, generally indicated at2414, may be changed using a write current 2412. As shown, the writecurrent represent a write 0 current that flows from the top electrode2402 through the free layer 2404, across the magnetic tunnel junctionbarrier 2406, through the fixed layer 2408, and through the bottomelectrode 2410.

FIG. 25 is a cross-sectional view 2500 of the MTJ stack of FIG. 23 takenalong line 25-25 in FIG. 23. The MTJ stack includes the first sidewall2302, the second sidewall 2306 and the bottom wall 2558. In thisexample, a direction of a first magnetic field carried by the free layerin the first sidewall 2302, as indicated at 2312, extends verticallyalong the first sidewall 2302 and in a direction corresponding to thearrow 2312. A direction of a second magnetic field carried by the freelayer of the second sidewall 2306, as indicated at 2316, extendsvertically along the second sidewall 2306 and in a directioncorresponding to the arrow 2316.

The MTJ stack includes a first domain barrier (wall) 2554 and a seconddomain barrier 2550. In a particular example, the second domain barrier2550 may correspond to a structural interface between the sidewall 2302and the bottom wall 2558. The second domain barrier 2550 isolates thefirst magnetic domain 2312 of the free layer of the first sidewall 2302from the fourth magnetic domain 2320 at the bottom wall 2558. The MTJstack also includes a third domain barrier 2556 and a fourth domainbarrier 2552. The fourth domain barrier 2552 may correspond to astructural interface between the bottom wall 2558 and the sidewall 2306.The fourth domain barrier 2552 isolates the magnetic field 2316 of afree layer of the sidewall 2306 from the magnetic field 2320 of the freelayer associated with the bottom wall 2558.

In the embodiment illustrated in FIG. 25, the MTJ stack may be adaptedto store at least three data bits. A first data bit may be representedby the first magnetic field 2312 carried by a free layer of the firstsidewall 2302. A second data bit may be represented by the fourthmagnetic field 2320 carried by a free layer of the bottom wall 2558. Athird data bit may be represented by the second magnetic field 2316carried by a free layer of the second sidewall 2306. The write currents2322, 2326, and 2330 may be applied to selectively alter an orientationof the magnetic field of a selected sidewall without altering theorientation of the magnetic field associated with the other sidewall orof the bottom wall 2558, for example.

FIG. 26 is a cross-sectional view 2600 of the MTJ stack of FIG. 23 takenalong line 26-26 in FIG. 23. In this particular example, the MTJ stackincludes magnetic domains barriers 2660 and 2662. The magnetic domainbarrier (or wall) 2662 isolates the magnetic domain 2318 carried by afree layer of the sidewall 2308 from the magnetic domain 2320 carried bya free layer of the bottom wall 2558.

In a particular illustrative embodiment, the domain barriers 2336 and2338 illustrated in FIG. 23, the domain barriers 2550 and 2552illustrated in FIG. 25, and the domain barrier 2662 illustrated in FIG.26 allow the MTJ stack to store multiple digital values. In particular,the MTJ stack illustrated in FIG. 23 may be adapted to store up to fourdigital values, which may be represented by the magnetic fields 2312,2316, 2318, and 2320, illustrated in FIGS. 23, 25, and 26. The fourdigital values may represent up to sixteen logic states.

FIG. 27 is a top view of a second illustrative embodiment of a magnetictunnel junction (MTJ) stack with multiple vertical magnetic domainswhere the MTJ cell is written in a bit one state. In this example, theMTJ stack 2700 is illustrated in a bit one state, where each of the bitsrepresents a logical one value. The MTJ stack 2700 includes a firstsidewall 2702, a second sidewall 2706, a third sidewall 2708, and abottom wall 2958 (depicted in FIG. 29). A sidewall opposite the thirdsidewall 2708 has been removed to form a U-shaped structure. Each of thesidewalls 2702, 2706, and 2708 and the bottom wall 2958 include a fixedlayer, a tunnel barrier, and a free layer. The free layers of each ofthe sidewalls 2702, 2706, and 2708 carry unique vertical magneticdomains and the free layer of the bottom wall 2958 carries a uniquemagnetic domain configured to represent a data value, such as a “1” or a“0” value. The first sidewall 2702 includes a free layer that carries avertical first magnetic domain 2712. The second sidewall 2706 includes afree layer that carries a vertical second magnetic domain 2716. Thethird sidewall 2708 includes a free layer that carries a vertical thirdmagnetic domain 2718. The bottom wall 2958 includes a free layer thatcarries a horizontal fourth magnetic domain 2720.

The first magnetic domain 2712 of the first sidewall 2702 is separatedfrom the third magnetic domain 2718 of the third sidewall 2708 by afirst domain barrier 2738. The second magnetic domain 2716 of the secondsidewall 2706 is also separated from the third magnetic domain 2718 ofthe third sidewall 2708 by a second domain barrier 2736. In general, thedomain barriers 2736 and 2738 represent domain walls, which areinterfaces that separate magnetic domains, such as the magnetic domains2712, 2716, and 2718. Such domain barriers 2736 and 2738 represent atransition between different magnetic moments. In a particularembodiment, the domain barriers 2736 and 2738 may represent a change ina magnetic moment where a magnetic field undergoes an angulardisplacement of 0 or 180 degrees.

The direction of a magnetic field associated with the first magneticdomain 2712 (i.e., a direction of a magnetic field within a free layer)in the first sidewall 2702 may be altered using a first write current2722. A direction of a magnetic field associated with the secondmagnetic domain 2716 that is carried by a free layer in the secondsidewall 2706 may be altered using a second write current 2726. Adirection of a magnetic field associated with the third magnetic domain2718 carried by a free layer of the third sidewall 2708 may be alteredusing a third write current 2728. A direction of a magnetic fieldassociated with the fourth magnetic domain 2720 carried by a free layerof the bottom wall 2958 may be altered using a fourth write current2730.

In general, a relative direction of the magnetic field carried by thefree layer relative to a fixed magnetic field in the fixed layer of eachof the sidewalls 2702, 2706, and 2708 determines the bit value stored bythat particular sidewall. In the example shown, the fixed layer and freelayer magnetic directions are antiparallel (as illustrated in bymagnetic fields 2814 and 2816 in FIG. 28). Accordingly, the writecurrents 2722, 2726, 2728, and 2730 may represent write “1” currents,placing the MTJ stack 2700 in a “1” state.

FIG. 28 is a diagram of a second illustrative embodiment of layers of amagnetic tunnel junction (MTJ) stack 2800 illustrating a write onecurrent flow direction. The MTJ structure 2800 includes a top electrode2802, a free layer 2804, a magnetic tunnel junction tunnel barrier 2806,a fixed layer 2808, and a bottom electrode 2810. The MTJ stack 2800 mayalso include an anti-ferromagnetic (AF) layer (not shown). In general,the top electrode 2802 and the bottom electrode 2810 are electricallyconductive layers adapted to carry an electrical current. The fixedlayer 2808 is a ferromagnetic layer that has been annealed, such as tobe pinned by an anti-ferromagnetic layer, to fix a direction of amagnetic field 2816 within the fixed layer 2808. The free layer 2804 isa ferromagnetic layer that can be programmed by a write current. The MTJtunnel barrier or barrier layer 2806 may be formed from an oxide barrierlayer (i.e., MgO, Al₂O₃, etc,) or other diamagnetic material. Thedirection of a magnetic field 2814 within the free layer 2804 may bechanged using the write current.

A direction of the magnetic fields in the free layer 2804 relative tothe fixed magnetic field of the fixed layer 2808 indicates whether thedata bit stored at the free layer 2804 of the particular MTJ cell 2800is a bit value of “1” or bit value of “0.” The magnetic direction of themagnetic field in the free layer 2804, generally indicated at 2814, maybe changed using a write current 2812. As shown, the write currentrepresent a write “1” current that flows from the bottom electrode 2810through the free fixed layer 2808, across the magnetic tunnel junctionbarrier 2806, through the free layer 2804, and through the top electrode2802.

FIG. 29 is a cross-sectional view 2900 of the MTJ stack of FIG. 27 takenalong line 29-29 in FIG. 27. The MTJ stack includes the first sidewall2702, the second sidewall 2706 and the bottom wall 2958. In thisexample, a direction of a first magnetic field carried by the free layerin the first sidewall 2702, as indicated at 2712, extends verticallyalong the first sidewall 2702 and in a direction corresponding to thearrow 2712. A direction of a second magnetic field carried by the freelayer of the second sidewall 2706, as indicated at 2716, extendsvertically along the second sidewall 2706 and in a directioncorresponding to the arrow 2716.

The MTJ stack includes a first domain barrier (wall) 2954 and a seconddomain barrier 2950. In a particular example, the second domain barrier2950 may correspond to a structural interface between the sidewall 2702and the bottom wall 2958. The second domain barrier 2950 isolates thefirst magnetic domain 2712 of the free layer of the first sidewall 2702from the fourth magnetic domain 2720 at the bottom wall 2958. The MTJstack also includes a third domain barrier 2956 and a fourth domainbarrier 2952. The fourth domain barrier 2952 may correspond to astructural interface between the bottom wall 2958 and the sidewall 2706.The fourth domain barrier 2952 isolates the magnetic field 2716 of afree layer of the sidewall 2706 from the magnetic field 2720 of the freelayer associated with the bottom wall 2958.

In the embodiment illustrated in FIG. 29, the MTJ stack may be adaptedto store at least three data bits that may represent up to eight logicalstates. A first data bit may be represented by the first magnetic field2712 carried by a free layer of the first sidewall 2702. A second databit may be represented by the fourth magnetic field 2720 carried by afree layer of the bottom wall 2958. A third data bit may be representedby the second magnetic field 2716 carried by a free layer of the secondsidewall 2706. The write currents 2722, 2726, and 2730 may be applied toselectively alter an orientation of the magnetic field of a selectedsidewall without altering the orientation of the magnetic fieldassociated with the other sidewall or of the bottom wall 2958, forexample.

FIG. 30 is a cross-sectional view 3000 of the MTJ stack of FIG. 27 takenalong line 30-30 in FIG. 27. In this particular example, the MTJ stackincludes magnetic domains barriers 3060 and 3062. The magnetic domainbarrier (or wall) 3062 isolates the magnetic domain 2718 carried by afree layer of the sidewall 2708 from the magnetic domain 2720 carried bya free layer of the bottom wall 2958.

In a particular illustrative embodiment, the domain barriers 2736 and2738 illustrated in FIG. 27, the domain barriers 2950 and 2952illustrated in FIG. 29, and the domain barrier 3062 illustrated in FIG.30 allow the MTJ stack to store multiple digital values. In particular,the MTJ stack illustrated in FIG. 27 may be adapted to store up to fourdigital values, which may be represented by the magnetic fields 2712,2716, 2718, and 2720, illustrated in FIGS. 27, 29, and 30. The fourdigital values may represent up to sixteen logical states

FIG. 31 is a diagram showing a cross-sectional view of a particularillustrative embodiment of a MTJ cell coupled to a bi-directional switchto read data from and to write data to the MTJ cell. The MTJ cell 3100may be utilized in a memory array including bit lines, such as a bitline 3108, and word lines, such as a word line 3110. The MTJ cell 3100includes a center electrode 3102, a magnetic tunnel junction stack 3104,and a bottom electrode 3106. The MTJ stack 3104 includes a fixed layer,a magnetic tunnel barrier, and a free layer that carries a programmablemagnetic domain, which orientation may be altered by applying a writecurrent to the MTJ cell 3100. Additional layers, such as ananti-ferromagnetic layer, may be also included. The MTJ stack 3104includes at least one vertical sidewall 3130 or 3132 and a horizontalbottom wall 3134. The bit line 3108 is coupled to the center electrode3102. The word line 3110 is coupled to a control terminal of a switch3116 that is coupled to the bottom electrode 3106 via a terminalstructure, illustrated by a line 3112, that is coupled to the bottomelectrode 3106 proximate to the bottom wall 3134. In a particularembodiment, the terminal structure may include a via, a contact, a bondpad, one or more other conductive structures coupled to the MTJ device3100, or any combination thereof.

In a particular embodiment, the switch 3116 may be a metal oxidesemiconductor field effect transistor (MOSFET), a transistor, or otherswitching circuit component. In another embodiment, the switch 3116 canbe a bi-directional switch to allow current flow both into and out ofthe MTJ cell 3100. The switch 3116 includes a first terminal coupled tothe line 3112, a control terminal coupled to the word line 3110, and asecond terminal coupled to a source line (SL), which may be coupled to apower source.

In a particular illustrative embodiment, a signal may be applied to thebit line 3108 and to the word line 3110 to activate the switch 3116.After activating the switch 3116, data may be read from the MTJ cell3100 based on a current flow through the MTJ cell 3100. For example, afixed voltage may be applied to the bit line 3108 and a voltage may beapplied to the word line 3110 to activate the switch 3116. A bit valuestored at the free layer of the MTJ stack 3104 may be determined basedon a current flow measured either at the bit line 3108 or at the sourceline 3118, for example. Because the switch 3116 is coupled to the bottomelectrode 3106 proximate to the bottom wall 3134, a read current may beprimarily determined by current through the bottom wall 3134. In thisparticular instance, the MTJ cell 3100 may store a single bit value. TheMTJ cell 3100 may be a memory cell within a memory array, such as amagneto-resistive random access memory (MRAM), an N-way cache, anon-volatile storage device, other memory devices, or any combinationthereof.

FIG. 32 is a diagram showing a cross-sectional view of a secondillustrative embodiment of a MTJ cell coupled to a bi-directional switchto read data from and to write data to the MTJ cell. The MTJ cell 3200may be utilized in a memory array including bit lines, such as a bitline 3208, and word lines, such as a word line 3210. The MTJ cell 3200includes a center electrode 3202, a magnetic tunnel junction stack 3204,and a bottom electrode 3206. The MTJ stack 3204 includes a fixed layer,a magnetic tunnel barrier, and a free layer that carries a programmablemagnetic domain, which orientation may be altered by applying a writecurrent to the MTJ cell 3200. Additional layers may be also included.The MTJ stack 3204 includes at least two vertical sidewalls 3230 and3232 and a horizontal bottom wall 3234. The bit line 3208 is coupled tothe center electrode 3202. The word line 3210 is coupled to a controlterminal of a switch 3216 that is coupled to the bottom electrode 3206via two terminal structures, illustrated by lines 3212 and 3214, thatare coupled to the bottom electrode 3206 proximate to the vertical sidewalls 3230 and 3232. In a particular embodiment, each terminal structuremay include a via, a contact, a bond pad, one or more other conductivestructures coupled to the MTJ device 3200, or any combination thereof.

In a particular embodiment, the switch 3216 may be a metal oxidesemiconductor field effect transistor (MOSFET), a transistor, or otherswitching circuit component. In another embodiment, the switch 3216 canbe a bi-directional switch to allow current flow both into and out ofthe MTJ cell 3200. The switch 3216 includes a first terminal coupled tothe lines 3212 and 3214, a control terminal coupled to the word line3210, and a second terminal coupled to a source line (SL), which may becoupled to a power source.

In a particular illustrative embodiment, a signal may be applied to thebit line 3208 and to the word line 3210 to activate the switch 3216.After activating the switch 3216, data may be read from the MTJ cell3200 based on a current flow through the MTJ cell 3200. For example, afixed voltage may be applied to the bit line 3208 and a voltage may beapplied to the word line 3210 to activate the switch 3216. A bit valuestored at the free layer of the MTJ stack 3204 may be determined basedon a current flow measured either at the bit line 3208 or at the sourceline, for example. Because the switch 3216 is coupled to the bottomelectrode 3206 proximate to the side walls 3230 and 3232, a read currentmay be primarily determined by current through the side wall 3230 and3232. In this particular instance, the MTJ cell 3200 may store a singlebit value. The MTJ cell 3200 may be a memory cell within a memory array,such as a magneto-resistive random access memory (MRAM), an N-way cache,a non-volatile storage device, other memory devices, or any combinationthereof.

FIG. 33 is a diagram showing a cross-sectional view of a magnetic tunneljunction (MTJ) cell with multiple vertical magnetic domains and coupledto two switches to read data from and to write data to the MTJ cell. TheMTJ cell 3300 includes a center electrode 3302, an MTJ structure 3304,and a bottom electrode 3306. The MTJ structure 3304 includes a fixedmagnetic layer, a magnetic tunnel junction barrier layer, and a freemagnetic layer. Additional layers may be also included. The freemagnetic layer carries a magnetic field that can be changed using awrite current to store a data value. The MTJ cell 3300 may be a memorycell within a memory array, such as a magneto-resistive random accessmemory (MRAM), an N-way cache, a non-volatile storage device, othermemory devices, or any combination thereof.

A bit line 3308 may be coupled to the center electrode 3302. A word line3310 may be coupled to control terminals of a first transistor 3314 andof a second transistor 3320. The first transistor 3314 includes a firstterminal coupled to the bottom electrode 3306 via a first terminalstructure depicted as a line 3312 and a second terminal 3316 coupled toa first source line (SL1), which may be coupled to a first power source.The second transistor 3320 includes a first terminal coupled to thebottom electrode 3306 via a second terminal structure depicted as a line3318 and includes a second terminal 3322 coupled to a second source line(SL2), which may be coupled to a second power source.

In a particular example, the transistor 3314 may be activated by theword line 3310 to provide a current path 3324 from the bit line 3308through the center electrode 3302, the MTJ structure 3304, the bottomelectrode 3306, the line 3312 and the transistor 3314 to the secondterminal 3316. Current flow via the current path 3324 indicates a “1”value or a “0” value stored at a magnetic domain associated with a sidewall 3330. Similarly, a current path provided via the line 3318 throughthe transistor 3320 may be used to access data stored via a magneticdomain adjacent to a sidewall 3340 of the MTJ cell 3300.

In general, to utilize multiple magnetic domains to store multiple datavalues in a single MTJ cell, such as the MTJ cell 3300, switches, suchas the switches 3314 and 3320, may be utilized to access the uniquemagnetic domains associated with the vertical sidewalls 3330 and 3340and the horizontal bottom wall 3350. An advantage of the MTJ cell 3300is that multiple vertical magnetic domains may be formed to allowmultiple digital values to be stored within a single cell, therebyincreasing storage density. Each of the multiple vertical magneticdomains includes a respective magnetic field orientation (direction)that can be modified by altering a current direction into or out of theMTJ cell 3300. In a particular example, each of the magnetic fields ofthe MTJ cell 3300 may be changed independently, without changing amagnetic orientation of other magnetic domains.

In a particular embodiment, because the source line 3316 and the sourceline 3322 are separated, it is possible to program the sidewall 3330without changing the magnetic field of the sidewall 3340. The bit line3308 and the word line 3310 may be utilized in conjunction with thesource lines 3316 and 3320 to separately change a direction of one orboth of the magnetic domains at the sidewalls 3330 and 3340 to storeindependent bit values.

FIG. 34 is a diagram showing a cross-sectional view of an MTJ cell withmultiple vertical magnetic domains and coupled to three switches to readdata from and to write data to the MTJ cell. The MTJ cell 3400 includesa center electrode 3402, an MTJ structure 3404, and a bottom electrode3406. The MTJ structure 3404 includes a fixed magnetic layer, a magnetictunnel junction barrier layer, and a free magnetic layer. The freemagnetic layer carries a magnetic field that can be changed using awrite current to store a data value. The MTJ cell 3400 may be a memorycell within a memory array, such as a magneto-resistive random accessmemory (MRAM), an N-way cache, a non-volatile storage device, othermemory devices, or any combination thereof.

A bit line 3408 may be coupled to the center electrode 3402. A word line3410 may be coupled to control terminals of a first transistor 3414, asecond transistor 3420, and a third transistor 3460. The firsttransistor 3414 includes a first terminal coupled to the bottomelectrode 3406 via a first terminal structure depicted as a line 3412and a second terminal 3416 coupled to a first source line (SL1), whichmay be coupled to a first power source. The second transistor 3420includes a first terminal coupled to the bottom electrode 3406 via asecond terminal structure depicted as a line 3418 and includes a secondterminal 3422 coupled to a second source line (SL2), which may becoupled to a second power source. The third transistor 3460 includes afirst terminal coupled to the bottom electrode 3406 via a third terminalstructure depicted as a line 3462 and includes a second terminal 3464coupled to a third source line (SL3), which may be coupled to a thirdpower source.

In a particular example, the transistor 3414 may be activated by theword line 3410 to provide a current path 3424 from the bit line 3408through the center electrode 3402, the MTJ structure 3404, the bottomelectrode 3406, the line 3412 and the transistor 3414 to the secondterminal 3416. Current flow via the current path 3424 indicates a “1”value or a “0” value stored at a vertical magnetic domain associatedwith the side wall 3430. Similarly, a current path provided via the line3418 through the transistor 3420 may be used to access data stored via avertical magnetic domain adjacent to the side wall 3440 of the MTJ cell3400. Likewise, the current path provided via the line 3462 through thetransistor 3460 may be used to access data stored via a horizontalmagnetic domain adjacent to the bottom wall 3450.

In general, to use multiple magnetic domains to store multiple datavalues in a single MTJ cell, such as the MTJ cell 3400, switches, suchas the switches 3414, 3420, and 3460 may be used to access the uniquemagnetic domains associated with the vertical sidewalls 3430 and 3440and the horizontal bottom wall 3450. An advantage of the MTJ cell 3400is that multiple vertical magnetic domains may be formed to allowmultiple bits to be stored within a single cell, thereby increasingstorage density. Each of the multiple vertical magnetic domains includesa respective magnetic field orientation (direction) that can be modifiedby altering a current direction into or out of the MTJ cell 3400. In aparticular example, each of the magnetic fields of the MTJ cell 3400 maybe changed independently, without changing a magnetic orientation ofother magnetic domains.

FIG. 35 is a diagram showing a cross-sectional view of a secondillustrative embodiment of a magnetic tunnel junction (MTJ) cell withmultiple vertical magnetic domains and coupled to three switches to readdata from and to write data to the MTJ cell. The MTJ cell 3500 includesa center electrode 3502, an MTJ structure 3504, and a bottom electrode3506. The MTJ structure 3504 includes a fixed magnetic layer, a magnetictunnel junction barrier layer, and a free magnetic layer. The freemagnetic layer carries a magnetic field that can be changed using awrite current to store a data value. The MTJ cell 3500 may be a memorycell within a memory array, such as a magneto-resistive random accessmemory (MRAM), an N-way cache, a non-volatile storage device, othermemory devices, or any combination thereof.

A bit line 3508 may be coupled to the center electrode 3502. A word line3510 may be coupled to control terminals of a first transistor 3514, asecond transistor 3520, and a third transistor 3560. The firsttransistor 3514 includes a first terminal coupled to the bottomelectrode 3506 via a first terminal structure that is proximate to afirst sidewall 3530 and depicted as a line 3512. The first transistor3514 includes a second terminal 3516 coupled to a first source line(SL1), which may be coupled to a first power source. The secondtransistor 3520 includes a first terminal coupled to the bottomelectrode 3506 via a second terminal structure that is proximate to asecond sidewall 3540 and depicted as a line 3518. The second transistor3520 includes a second terminal 3522 coupled to a second source line(SL2), which may be coupled to a second power source. The thirdtransistor 3560 includes a first terminal coupled to the bottomelectrode 3506 via a third terminal structure that is proximate to athird sidewall 3550 (located behind the center electrode 3502 andindicated as a broken line) and depicted as a line 3562. The thirdtransistor 3560 includes a second terminal 3564 coupled to a thirdsource line (SL3), which may be coupled to a third power source.

In a particular example, the transistor 3514 may be activated by theword line 3510 to provide a current path from the bit line 3508 throughthe center electrode 3502, the MTJ structure 3504, the bottom electrode3506, the line 3512 and the transistor 3514 to the second terminal 3516.Current flow through the transistor 3514 may indicate a “1” value or a“0” value stored at a vertical magnetic domain associated with the sidewall 3530. Similarly, a current path provided via the line 3518 throughthe transistor 3520 may be used to access data stored via a verticalmagnetic domain adjacent to the side wall 3540 of the MTJ cell 3500.Likewise, the current path provided via the line 3562 through thetransistor 3560 may be used to access data stored via a verticalmagnetic domain adjacent to the third sidewall 3550.

In general, to use multiple magnetic domains to store multiple datavalues in a single MTJ cell, such as the MTJ cell 3500, switches, suchas the switches 3514, 3520, and 3560 may be used to access the uniquemagnetic domains associated with the vertical sidewalls 3530, 3540, and3550. An advantage of the MTJ cell 3500 is that multiple verticalmagnetic domains may be formed to allow multiple bits to be storedwithin a single cell, thereby increasing storage density. Each of themultiple vertical magnetic domains includes a respective magnetic fieldorientation (direction) that can be modified by altering a currentdirection into or out of the MTJ cell 3500. In a particular example,each of the magnetic fields of the MTJ cell 3500 may be changedindependently, without changing a magnetic orientation of other magneticdomains.

FIG. 36 is a diagram showing a cross-sectional view of a magnetic tunneljunction (MTJ) cell with multiple vertical magnetic domains and coupledto four switches to read data from and to write data to the MTJ cell.The MTJ cell 3600 includes a center electrode 3602, an MTJ structure3604, and a bottom electrode 3606. The MTJ structure 3604 includes afixed magnetic layer, a magnetic tunnel junction barrier layer, and afree magnetic layer. The MTJ structure 3604 may also include ananti-ferromagnetic (AF) layer, other additional layers, or anycombination thereof. The free magnetic layer carries a magnetic fieldthat can be changed using a write current to store a data value. The MTJcell 3600 may be a memory cell within a memory array, such as amagneto-resistive random access memory (MRAM), an N-way cache, anon-volatile storage device, other memory devices, or any combinationthereof.

A bit line 3608 may be coupled to the center electrode 3602. A word line3610 may be coupled to control terminals of a first transistor 3614, asecond transistor 3620, a third transistor 3660, and a fourth transistor3692. The first transistor 3614 includes a first terminal coupled to thebottom electrode 3606 via a first terminal structure that is proximateto a first sidewall 3630 and depicted as a line 3612. The firsttransistor 3614 includes a second terminal 3616 coupled to a firstsource line (SL1), which may be coupled to a first power source. Thesecond transistor 3620 includes a first terminal coupled to the bottomelectrode 3606 via a second terminal structure that is proximate to asecond sidewall 3640 and depicted as a line 3618. The second transistor3620 includes a second terminal 3622 coupled to a second source line(SL2), which may be coupled to a second power source. The thirdtransistor 3660 includes a first terminal coupled to the bottomelectrode 3606 via a third terminal structure that is proximate to athird sidewall 3650 (located behind the center electrode 3602 andindicated as a broken line) and depicted as a line 3662. The thirdtransistor 3660 includes a second terminal 3664 coupled to a thirdsource line (SL3), which may be coupled to a third power source. Thefourth transistor 3692 includes a first terminal coupled to the bottomelectrode 3606 via a fourth terminal structure that is proximate to abottom wall 3690 and depicted as a line 3694. The fourth transistor 3692includes a second terminal 3696 coupled to a fourth source line (SL4),which may be coupled to a fourth power source.

In a particular example, the transistor 3614 may be activated by theword line 3610 to provide a current path from the bit line 3608 throughthe center electrode 3602, the MTJ structure 3604, the bottom electrode3606, the line 3612 and the transistor 3614 to the second terminal 3616.Current flow through the transistor 3614 may indicate a “1” value or a“0” value stored at a vertical magnetic domain associated with the sidewall 3630. Similarly, a current path provided via the line 3618 throughthe transistor 3620 may be used to access data stored via a verticalmagnetic domain adjacent to the side wall 3640 of the MTJ cell 3600.Likewise, the current path provided via the line 3662 through thetransistor 3660 may be used to access data stored via a verticalmagnetic domain adjacent to the third sidewall 3650. In addition, thecurrent path provided via the line 3694 through the transistor 3692 maybe used to access data stored via the horizontal magnetic domainadjacent to the bottom wall 3690.

In general, to use multiple magnetic domains to store multiple datavalues in a single MTJ cell, such as the MTJ cell 3600, switches, suchas the switches 3614, 3620, 3660, and 3692 may be used to access theunique magnetic domains associated with the vertical sidewalls 3630,3640, and 3650 and the horizontal bottom wall 3690. An advantage of theMTJ cell 3600 is that multiple vertical magnetic domains may be formedto allow multiple bits to be stored within a single cell, therebyincreasing storage density. Each of the multiple vertical magneticdomains and the horizontal magnetic domain includes a respectivemagnetic field orientation (direction) that can be modified by alteringa current direction into or out of the MTJ cell 3600. In a particularexample, each of the magnetic fields of the MTJ cell 3600 may be changedindependently, without changing a magnetic orientation of other magneticdomains.

FIG. 37 is a flow diagram of a particular illustrative embodiment of amethod of fabricating a magnetic tunnel junction (MTJ) device withmultiple vertical magnetic domains. In a particular embodiment, themethod may be used during fabrication of MTJ devices such as illustratedin FIG. 4 or FIG. 5. In general, a depth of a trench for formation ofthe MTJ structure is tightly controlled. The MTJ film deposit is madeand the top electrode thickness is controlled to form narrow turn gapswithout seams. The magnetic anneal process is applied in two dimensionsalong a horizontal dimension and a vertical direction to initialize thebottom and the vertical magnetic domains with a fixed magnetic fielddirection. By controlling the shape of the cell and the depth of thecell, such that the depth is greater than the width and the length, adirection of the magnetic fields within the MTJ cell may be controlled.In a particular example, a large aspect ratio of the depth to width andlength can make the bottom MTJ and the sidewall MTJ magnetic domainsmore isotropic. In a particular embodiment, a MTJ stack structure isdefined by a deep trench, and MTJ photo and etch processes that may becritical or expensive may be avoided. The trench photo and etch processmay be more easily controlled than a MTJ photo and etch process,resulting in lower costs and improved performance.

At 3702, a deep trench is formed in a semiconductor substrate. In aparticular embodiment, the trench depth is greater than the trenchlength and width so that the MTJ device will have at least one verticalmagnetic domain. Moving to 3704, a cap film layer is deposited.Continuing to 3706, a bottom electrode is deposited within the deeptrench. Advancing to 3708, multiple magnetic tunnel junction (MTJ) filmlayers are deposited, including a magnetic film layer and a tunnelbarrier layer.

Proceeding to 3710, a top electrode is deposited. Moving to 3712, a MTJhardmask is deposited. Continuing to 3714, a magnetic anneal isperformed in a horizontal X direction and in a vertical Y direction.Advancing to 3716, the substrate is patterned and etched at a depth tostop at the bottom electrode and a photoresist (PR) strip and cleanprocess is performed. Proceeding to 3718, a bottom electrode photo/etchprocess is performed with a PR strip process is performed. Moving to3720, a cap film layer is deposited.

Continuing to 3722, an inter-layer dielectric layer is deposited.Proceeding to 3724, a chemical mechanical polishing (CMP) operation isperformed. Moving to 3726, a via photo/etch/fill and polish operation isperformed.

FIG. 38 is a flow diagram of a second particular illustrative embodimentof a method of fabricating a magnetic tunnel junction (MTJ) device withmultiple vertical magnetic domains. In a particular embodiment, themethod may be used during fabrication of MTJ devices such as illustratedin FIG. 6.

At 3802, a cap film layer is deposited. Moving to 3804, a bottom viaphoto/etch/fill and chemical mechanical polishing (CMP) process isperformed. Continuing to 3806, an inter-layer dielectric (ILD) layer isdeposited and a CMP process is performed.

At 3808, a deep trench is formed in a semiconductor substrate. In aparticular embodiment, the trench depth is greater than the trenchlength and width so that the MTJ device will have at least one verticalmagnetic domain. Continuing to 3810, a bottom electrode is depositedwithin the deep trench. Advancing to 3812, multiple magnetic tunneljunction (MTJ) film layers are deposited, including a magnetic filmlayer and a tunnel barrier layer.

Proceeding to 3814, a top electrode is deposited. Moving to 3816, an MTJhardmask is deposited. Continuing to 3818, a magnetic anneal isperformed in a horizontal X direction and in a vertical Y direction.Advancing to 3820, the substrate is patterned and etched at a depth tostop at the bottom electrode. Proceeding to 3822, a bottom electrodephoto/etch process is performed. In a particular embodiment, such asduring fabrication of the MTJ device illustrated in FIG. 31, the photoand etch process for the MTJ device and the bottom electrode may becombined.

Moving to 3824, a cap film layer is deposited. Advancing to 3826, aninter-layer dielectric layer is deposited. Proceeding to 3828, achemical mechanical polishing (CMP) operation is performed. Moving to3830, a via photo/etch/fill and polish operation is performed.

FIG. 39 is a flow diagram of a third particular illustrative embodimentof a method of fabricating a magnetic tunnel junction (MTJ) device withmultiple vertical magnetic domains. In a particular embodiment, themethod may be used during fabrication of MTJ devices such as illustratedin FIGS. 15-22.

At 3902, bottom metal wire is deposited and patterning is performed. Ifa Damascene process is used, a bottom metal and a via process may becombined. Moving to 3904, an inter-layer dielectric (IDL) layer isdeposited, a chemical mechanical polishing (CMP) is performed, and a capfilm is deposited. Proceeding to 3906, a determination is made whetherthe MTJ device includes a bottom via connection, such as depicted inFIGS. 19-22. Continuing to 3908, when the MTJ device includes a bottomvia connection, the bottom via is opened, filled, and a via CMP isperformed. When the MTJ device does not include a bottom via connection,the method proceeds to 3910, where an inter-layer dielectric film isdeposited and a cap film are deposited. Proceeding to 3912, adetermination is made whether the MTJ device includes a sidewall bottomvia connection, such as depicted in FIGS. 17-18. Continuing to 3914,when the MTJ device includes a sidewall bottom via connection, thesidewall bottom via is opened, filled, and a via CMP is performed. Whenthe MTJ device does not include a sidewall bottom via connection, themethod proceeds to 3916.

Moving to 3916, the MTJ trench is patterned and etched to the cap layer,stripped, and cleaned. Continuing to 3918, a bottom electrode isdeposited, the MTJ film is deposited, and a top electrode is deposited.Advancing to 3920, a MTJ hardmask is deposited, a photo/etch process isperformed to stop at the bottom electrode, photo resist stripped, andcleaned. Proceeding to 3922, a photo/etch process of the bottomelectrode is performed with photo resist strip and clean.

Moving to 3924, a MTJ sidewall mask photo/etch process is performed toremove one side wall, photo resist stripped, and cleaned. Continuing to3926, a cap film layer is deposited. Advancing to 3928, an inter-layerdielectric film is deposited and a CMP performed. Proceeding to 3930, atop via open/etch and clean process is performed, the via is filled, anda via CMP is performed. Moving to 3932, top metal wire is deposited andpatterned. If damascene process is existed, the via process of 3930 viaand the metal process of 3932 can be combined.

FIG. 40 is a flow diagram of a particular illustrative embodiment of amethod of operating an MTJ device with multiple vertical magneticdomains. At 4002, the method includes selectively activating a bit linecoupled to a center electrode of a magnetic tunnel junction structureincluding a plurality of sidewalls, where each of the plurality ofsidewalls includes a free layer to carry a unique vertical magneticdomain. Continuing to 4004 one or more bidirectional switches areselectively activated to allow current flow through the MTJ structure,where the one or more bi-directional switches are coupled to respectivesidewalls of a plurality of sidewalls and coupled to a power source.Moving to 4006, during a read operation, a data value associated witheach of the unique vertical magnetic domains is determined based on aresistance associated with the current path. Proceeding to 4008, duringa write operation, a current direction through the MTJ structure iscontrolled via each of the one or more switches to selectively control amagnetic correction within the free layer of selective magnetic domains,where the magnetic direction is related to a data value. The methodterminates at 4010.

FIG. 41 is a block diagram of a communications device 4100 including amemory device including multiple magnetic tunnel junction (MTJ) cells.The communications device 4100 includes a memory array of MTJ cells 4132and a cache memory of MTJ cells 4164, which are coupled to a processor,such as a digital signal processor (DSP) 4110. The communications device4100 also includes a magneto-resistive random access memory (MRAM)device 4166 that is coupled to the DSP 4110. In a particular example,the memory array of MTJ cells 4132, the cache memory of MTJ cells 4164,and the MRAM device 4166 include multiple MTJ cells, where each MTJ cellincludes at least one vertical domain and is adapted to store multipleindependent digital values, as described with respect to FIGS. 1-21.

FIG. 41 also shows a display controller 4126 that is coupled to thedigital signal processor 4110 and to a display 4128. A coder/decoder(CODEC) 4134 can also be coupled to the digital signal processor 4110. Aspeaker 4136 and a microphone 4138 can be coupled to the CODEC 4134.

FIG. 41 also indicates that a wireless controller 4140 can be coupled tothe digital signal processor 4110 and to a wireless antenna 4142. In aparticular embodiment, an input device 4130 and a power supply 4144 arecoupled to the on-chip system 4122. Moreover, in a particularembodiment, as illustrated in FIG. 41, the display 4128, the inputdevice 4130, the speaker 4136, the microphone 4138, the wireless antenna4142, and the power supply 4144 are external to the on-chip system 4122.However, each can be coupled to a component of the on-chip system 4122,such as an interface or a controller.

Those of skill would further appreciate that the various illustrativelogical blocks, configurations, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, configurations,modules, circuits, and steps have been described above generally interms of their functionality. Whether such functionality is implementedas hardware or software depends upon the particular application anddesign constraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

The steps of a method or algorithm described in connection with theembodiments disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, MRAM memory, flash memory,ROM memory, PROM memory, EPROM memory, EEPROM memory, registers, harddisk, a removable disk, a CD-ROM, or any other form of storage mediumknown in the art. An exemplary storage medium is coupled to theprocessor such that the processor can read information from, and writeinformation to, the storage medium. In the alternative, the storagemedium may be integral to the processor. The processor and the storagemedium may reside in an ASIC. The ASIC may reside in a computing deviceor a user terminal. In the alternative, the processor and the storagemedium may reside as discrete components in a computing device or userterminal.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the disclosedembodiments. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the disclosure. Thus, the present disclosure is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope possible consistent with the principles andnovel features as defined by the following claims.

1. A magnetic tunnel junction (MTJ) structure comprising: a MTJ cellcomprising multiple vertical side walls, each of the multiple verticalside walls defining a unique vertical magnetic domain, each of theunique vertical magnetic domains adapted to store a digital value. 2.The MTJ structure of claim 1, wherein a first of the vertical side wallsis separated from a second of the vertical side walls by a distance thatis less than a height of the first vertical side wall.
 3. The MTJstructure of claim 1, wherein the MTJ cell further comprises a centerelectrode extending vertically between the multiple vertical side walls.4. The MTJ structure of claim 3, wherein a thickness of the centerelectrode is approximately half of a difference between a width of theMTJ cell minus a width of two opposing side walls of the multiplevertical side walls.
 5. The MTJ structure of claim 1, wherein the MTJcell comprises a first vertical side wall having a first magneticdomain, a second vertical sidewall having a second magnetic domain and athird vertical sidewall having a third magnetic domain.
 6. The MTJstructure of claim 5, wherein the MTJ cell further comprises a bottomwall coupled to the multiple vertical side walls, the bottom wall havinga fourth magnetic domain.
 7. The MTJ structure of claim 6, furthercomprising four terminal structures, wherein three of the four terminalstructures are coupled to the vertical side walls and a fourth of thefour terminal structures is coupled to the bottom wall.
 8. The MTJstructure of claim 1, wherein the MTJ cell is U-shaped.
 9. The MTJstructure of claim 1, wherein the MTJ cell comprises four vertical sidewalls in a substantially rectangular shape.
 10. The MTJ structure ofclaim 9, wherein the MTJ cell further comprises a bottom wall coupled tothe four vertical side walls.
 11. The MTJ structure of claim 10, whereinthe MTJ structure further comprises six terminal structures.
 12. Adevice comprising: a single magnetic tunnel junction (MTJ) cell adaptedto store multiple digital values, wherein at least one of the multipledigital values is stored using a vertical magnetic field; and multipleterminals coupled to the MTJ cell.
 13. The device of claim 12, furthercomprising a transistor coupled to a first of the multiple terminals,the transistor also coupled to a data write line and to a first sourceline.
 14. The device of claim 13, further comprising a second transistorcoupled to a second of the multiple terminals, the second transistorcoupled to the data write line and coupled to a second source line. 15.The device of claim 14, further comprising a third transistor coupled toa third of the multiple terminals, the third transistor coupled to thedata write line and coupled to a third source line.
 16. The device ofclaim 15, wherein the first of the multiple terminals is coupled to afirst sidewall of the MTJ cell, the second of the multiple terminals iscoupled to a second sidewall of the MTJ cell, and the third of themultiple terminals is coupled to a bottom wall of the MTJ cell.
 17. Thedevice of claim 16, further comprising a fourth of the multipleterminals coupled to a bit line.
 18. A method of fabricating a device,the method comprising: performing a deep trench photo and etch processto create a deep trench in a substrate; depositing a bottom electrodeinto the deep trench; depositing layers to form a magnetic tunneljunction (MTJ) structure including a fixed layer, a tunnel barrier, anda free layer, at least a first portion of the MTJ structure coupled tothe bottom electrode; depositing a top electrode onto at least a secondportion of the MTJ structure; and performing magnetic anneal process onthe MTJ structure in a horizontal direction and in a vertical direction,the horizontal direction substantially parallel to a plane of thesubstrate and the vertical direction substantially normal to the planeof the substrate; wherein a first portion of the free layer has a firstmagnetic domain in the vertical direction and wherein a second portionof the free layer has a second magnetic domain in the horizontaldirection.
 19. The method of claim 18, further comprising performing aninter-layer dielectric (ILD) deposit and performing a chemicalmechanical polish (CMP) process.
 20. The method of claim 19, furthercomprising performing photoresist, etching, filling, and CMP processeson a via coupled to the MTJ.
 21. The method of claim 18, wherein the MTJstructure includes a first sidewall in the vertical direction and asecond sidewall in the vertical direction.
 22. The method of claim 21,further comprising: depositing a cap film layer; performing a process toetch, fill, and polish a bottom via; and depositing an inter-layerdielectric layer.
 23. The method of claim 18, wherein the MTJ structurehas a U-shape.
 24. The method of claim 18, wherein the trench has adepth greater than a height of a sidewall of the MTJ structure, whereinthe height of the sidewall is greater than a length of the trench andgreater than a width of the trench.